feat(12-01): add Laravel request validation to lagoon

- lagoon.ValidateRequest ports Laravel 9 request validation: wildcard
  expansion, implicit-rule stop, bail, sometimes/nullable/blank skipping,
  size messages split by type and character-counted string lengths
- ParseRules, In, CustomRule, UploadedFile and ErrorKeys for rule tables
- pl/en lagoon::validation catalogs ported verbatim from WinterCMS
- lagoon.Validate answers a numeric range failure with the bound that
  failed (min, max or numeric between) instead of always max

modules/lagoon/README.md

@@ -17,7 +17,8 @@ Postgres data layer: the shared GORM connection, per-plugin migrations, model he
 - After-commit work: `lagoon.Transaction` runs a function in a transaction and then the callbacks registered with `lagoon.AfterCommit`, in order, only after the commit succeeds; a nested `lagoon.Transaction` is a savepoint whose callbacks are dropped with it when it fails. A nested `lagoon.Transaction` must be given the outer transaction's handle: given a root handle it returns an error without running its function, rather than open an independent transaction whose callbacks would wait on the outer one. A single-statement write for which GORM opens its own implicit transaction runs its callbacks from `lagoon:after_commit` once GORM commits, and never when the write fails. A callback registered inside a foreign plain GORM transaction is unsafe because Lagoon cannot observe its commit, so `lagoon.AfterCommit` warns and skips it. Outside a transaction, callbacks run immediately. The handle a supported callback receives always has an empty statement on the connection its work belongs to. A panicking callback is logged and never turns a committed write into an error.
 - Per-plugin migrations: `lagoon.Migrate` runs the framework's `system_files` set (`attach.Migrations`), backend admin identity set (`lagoon.BackendAdminMigrations`) and job-queue set (`lagoon.QueueMigrations`: River's schema pinned at `lagoon.RiverSchemaVersion`, then the `lagoon.JobsTable` record table, under the `lagoon.QueueHistoryID` history), then every `pact.HasMigrations` set in plugin activation order, each in its own `summer_migrations_<plugin_id>` history table (`lagoon.HistoryTableName`). `lagoon.RollbackLast` and `lagoon.Status` cover rollback and history.
 - Mass assignment: `lagoon.Fill` copies only allow-listed keys onto a model by GORM column name and silently drops the rest, logging each dropped key once outside production. A `json.Number` (from a decoder using `UseNumber`) fills integer, unsigned and float fields. A value that does not fit its column (a fraction, an exponent or an overflow for an integer field, or a value of the wrong type) is a `lagoon.FillTypeError` naming the key, so a caller can answer it as a validation failure on that field. `lagoon.HasFillable` and `lagoon.HasHidden` are the Go forms of `$fillable` and `$hidden`.
-- Validation: `lagoon.Validate` accepts Laravel-style rule strings (`required`, `nullable`, `integer`, `numeric`, `between`, `min`, `max`, `in`, `unique`, `boolean`, `email`, `confirmed`, `different`, `mimes`) and returns a field-to-messages map, translated through phrasebook when a translator is given. Unknown rule tokens are an error.
+- Validation: `lagoon.Validate` accepts Laravel-style rule strings (`required`, `nullable`, `integer`, `numeric`, `between`, `min`, `max`, `in`, `unique`, `boolean`, `email`, `confirmed`, `different`, `mimes`) and returns a field-to-messages map, translated through phrasebook when a translator is given. Unknown rule tokens are an error. A failed numeric range reports the bound that failed: the `min` message below the lower bound, the `max` message above the upper one, and the numeric `between` message when the bound came from `between`.
+- Request validation: `lagoon.ValidateRequest` reproduces Laravel 9 request validation for ported API endpoints, so a 422 body matches the PHP one message for message. It takes the decoded input and an ordered `lagoon.RequestRule` table (attribute names may hold `*` wildcards, expanded against the input to `posts.0.title`), runs the rules of each attribute in order and stops an attribute after a failed implicit rule (`required`, `present`, `filled`, `accepted`) or, under `bail`, after any failure. A non-implicit rule is skipped for an absent attribute, a blank string, a null value under `nullable` and an absent key under `sometimes`. Supported rules: `required`, `present`, `filled`, `accepted`, `nullable`, `sometimes`, `bail`, `array`, `string`, `integer`, `numeric`, `boolean`, `email` (PHP `FILTER_VALIDATE_EMAIL`, WinterCMS's default), `url`, `date`, `after`, `after_or_equal`, `before`, `before_or_equal` (a date, a relative word such as `tomorrow`, or another field), `exists:table,column`, `regex`, `not_regex`, `in`, `not_in`, `file`, `image`, `mimes`, `min`, `max`, `size` and `between`, plus closure rules built with `lagoon.CustomRule`. The size rules compare the number under `numeric` or `integer` (exactly, as decimals), the element count of an array, kilobytes of a `lagoon.UploadedFile`, and otherwise the length in characters, and pick the matching message. Messages come from the `lagoon::validation` catalog in the request locale; `lagoon.ErrorKeys` gives the attribute order of PHP's message bag.
 - Safe ordering: `lagoon.OrderBy` appends an ORDER BY only for an allow-listed column and an `asc` or `desc` direction, and `lagoon.Collate` adds a validated `COLLATE` clause for language-specific text order (for example the ICU collation `pl-x-icu`); lagoon puts no requirement on the database's default locale.
 - Pagination: `lagoon.Paginate` builds a `lagoon.Page` with `data` and `meta` (`current_page`, `last_page`, `per_page`, `total`).
 - Column types: `lagoon.Encrypted` stores AES-256-GCM ciphertext under a key derived from `app.key`, decrypts with previous keys during rotation, and always redacts itself in JSON and string output; `lagoon.Jsonable` stores JSON as TEXT and keeps SQL NULL distinct from an empty value.
@@ -135,6 +136,14 @@ func (p *Plugin) Migrations() []*gormigrate.Migration {
 | `lagoon.Fill` | Allow-listed mass assignment by column name. |
 | `lagoon.FillTypeError` | Returned by `lagoon.Fill` when a requested value does not fit its column; `Key` names the column. |
 | `lagoon.Validate` | Laravel-style rule validation with a `unique` database check. |
+| `lagoon.ValidateRequest` | Laravel 9 request validation of decoded input against an ordered rule table; returns Laravel's errors object. |
+| `lagoon.RequestRule` | One attribute of a request rule table: `Field` (wildcards allowed) and its ordered `Rules`. |
+| `lagoon.Rule` | One parsed rule; `lagoon.Rule.Name` and `lagoon.Rule.Args` describe it. |
+| `lagoon.ParseRules` | Parses a Laravel rule string into rules; keeps `regex:` patterns whole and panics on an unknown rule or an invalid pattern, so rule tables fail at boot. |
+| `lagoon.In` | The `in` rule from a list of values, for values that contain commas or quotes (Laravel's `Rule::in`). |
+| `lagoon.CustomRule` | A closure rule; its failure message is used as written. |
+| `lagoon.UploadedFile` | An uploaded file for the file rules; `lagoon.UploadedFileFromHeader` adapts a `multipart.FileHeader`. |
+| `lagoon.ErrorKeys` | The attributes of an errors object in Laravel's order for a rule table. |
 | `lagoon.OrderBy` | Allow-listed ORDER BY, with an optional `lagoon.Collate`. |
 | `lagoon.Collate` | Order option that sorts the column with a named PostgreSQL collation; the name is validated and quoted. |
 | `lagoon.OrderOption` | Option type accepted by `lagoon.OrderBy`. |