feat: Organisations admin screen with the avatar and the members manager

- controller golem15.user.organisations behind golem15.users.access_users
- list and form (name, slug preset from the name, description, avatar)
- members relation manager: link sets and unlink clears users.organisation_id
- deleting an organisation releases its members first
- Organisation gains Fillable, Rules, MorphName, AttachRelations, BeforeValidate
  and the Members relation; models.Slugify
- navigation side item organisations
- TestAdminOrganisations, TestAdminOrganisationMembers, TestSlugify

models/organisation.go

@@ -1,9 +1,16 @@
 package models
 
-import "time"
+import (
+	"time"
 
-// Organisation is the structure-only FK target for Fonoteka org credentials.
-// Roles and membership behavior belong to Phase 7 AUTH-02.
+	"git.golem15.com/golem15/summercms/modules/lagoon/attach"
+	"gorm.io/gorm"
+)
+
+// Organisation is a row of golem15_user_organisations, the PHP Organisation
+// model: a named group of users (users.organisation_id) that other plugins
+// hang organisation-level data on. The table is shared with those plugins
+// and gets no column from the admin screen.
 type Organisation struct {
 	ID          uint      `gorm:"column:id;primaryKey"`
 	Slug        string    `gorm:"column:slug"`
@@ -11,10 +18,50 @@ type Organisation struct {
 	Description *string   `gorm:"column:description"`
 	CreatedAt   time.Time `gorm:"column:created_at"`
 	UpdatedAt   time.Time `gorm:"column:updated_at"`
+	// Members is the PHP hasMany members relation: the users whose
+	// organisation_id is this organisation. It is not a column. It is loaded
+	// only on request, written only by the admin members manager (which sets
+	// and clears users.organisation_id), and never serialized.
+	Members []User `gorm:"foreignKey:OrganisationID;references:ID" json:"-"`
 }
 
 func (Organisation) TableName() string { return "golem15_user_organisations" }
 
+// MorphName is the PHP class string stored in system_files.attachment_type.
+func (Organisation) MorphName() string { return `Golem15\User\Models\Organisation` }
+
+// OrganisationAvatarField is the attachOne relation name of the
+// organisation's picture.
+const OrganisationAvatarField = "avatar"
+
+// AttachRelations declares the public attachOne avatar (PHP $attachOne).
+func (Organisation) AttachRelations() []attach.Relation {
+	return []attach.Relation{{Name: OrganisationAvatarField, Public: true}}
+}
+
+// Fillable is the PHP $fillable list.
+func (Organisation) Fillable() []string {
+	return []string{"name", "slug", "description"}
+}
+
+// Rules is the PHP rule set without alpha_dash on slug, which the rule
+// engine does not know: the admin controller checks the slug's characters.
+func (Organisation) Rules() map[string]string {
+	return map[string]string{
+		"name":        "required|max:255",
+		"slug":        "required|unique:golem15_user_organisations",
+		"description": "nullable|max:5000",
+	}
+}
+
+// BeforeValidate fills an empty slug from the name, the PHP beforeValidate.
+func (o *Organisation) BeforeValidate(_ *gorm.DB) error {
+	if o.Slug == "" && o.Name != "" {
+		o.Slug = Slugify(o.Name)
+	}
+	return nil
+}
+
 func init() {
 	Register(Organisation{})
 }