feat: pagination forms and suffixes in resolve and site

- Pagination tab: query or path form, per-locale segment, title and
  description suffixes with %page% and %pages%
- ?page=1, /<segment>/1 and the other form answer 301 to the configured
  address in one hop with normalisation and strict URLs; a page value
  that is not a number answers not_found with pagination.invalid
- page 2 and later: self canonical with the page, index,follow, the
  suffixes (%pages% left for the layer), paged hreflang alternates
- GET /site answers pagination {form, param, segments} and home_crumb

models/settings/fields.yaml

@@ -4,7 +4,7 @@
 #
 # SEO settings (UI-SPEC C11, C20): General, one tab per content type (added
 # by the plugin's form extension after General), Indexing, Addresses,
-# Links, Publisher, Local business and Verification.
+# Pagination, Links, Publisher, Local business and Verification.
 
 fields:
     _staging:
@@ -146,6 +146,38 @@ fields:
         default: false
         tab: golem15.seo::lang.settings.tab_urls
 
+    page_form:
+        label: golem15.seo::lang.settings.page_form
+        comment: golem15.seo::lang.settings.page_form_comment
+        type: dropdown
+        span: left
+        default: query
+        options:
+            query: golem15.seo::lang.settings.page_form_query
+            path: golem15.seo::lang.settings.page_form_path
+        tab: golem15.seo::lang.settings.tab_pagination
+
+    page_segment:
+        label: golem15.seo::lang.settings.page_segment
+        comment: golem15.seo::lang.settings.page_segment_comment
+        type: mltext
+        span: right
+        tab: golem15.seo::lang.settings.tab_pagination
+
+    page_title_suffix:
+        label: golem15.seo::lang.settings.page_title_suffix
+        comment: golem15.seo::lang.settings.page_title_suffix_comment
+        type: mltext
+        span: left
+        tab: golem15.seo::lang.settings.tab_pagination
+
+    page_description_suffix:
+        label: golem15.seo::lang.settings.page_description_suffix
+        comment: golem15.seo::lang.settings.page_description_suffix_comment
+        type: mltext
+        span: right
+        tab: golem15.seo::lang.settings.tab_pagination
+
     links_new_tab:
         label: golem15.seo::lang.settings.links_new_tab
         comment: golem15.seo::lang.settings.links_new_tab_comment