Add Django's custom Sphinx roles and use them to link to settings

This is necessary for rST docs, i.e. in docstrings and in eval-rst
blocks. Without this, Sphinx cannot seem to understand the role. See:
https://stackoverflow.com/questions/13387125

MyST-Parser seems to be smarter, it can figure out these custom
roles without having to register the types ourselves. This is evident in
the previous commits where I already use the :setting: role in markdown
docs.

docs/conf.py

@@ -365,3 +365,26 @@ epub_copyright = copyright
 
 def setup(app):
     app.add_js_file("js/banner.js")
+
+    # Django-specific roles, from
+    # https://github.com/django/django/blob/main/docs/_ext/djangodocs.py:
+    app.add_crossref_type(
+        directivename="setting",
+        rolename="setting",
+        indextemplate="pair: %s; setting",
+    )
+    app.add_crossref_type(
+        directivename="templatetag",
+        rolename="ttag",
+        indextemplate="pair: %s; template tag",
+    )
+    app.add_crossref_type(
+        directivename="templatefilter",
+        rolename="tfilter",
+        indextemplate="pair: %s; template filter",
+    )
+    app.add_crossref_type(
+        directivename="fieldlookup",
+        rolename="lookup",
+        indextemplate="pair: %s; field lookup type",
+    )

docs/reference/streamfield/blocks.md

@@ -189,7 +189,7 @@ All block definitions accept the following optional keyword arguments:
 
     A date picker. The following keyword arguments are accepted in addition to the standard ones:
 
-    :param format: Date format. This must be one of the recognized formats listed in the `DATE_INPUT_FORMATS <https://docs.djangoproject.com/en/stable/ref/settings/#std:setting-DATE_INPUT_FORMATS>`_ setting. If not specified Wagtail will use the ``WAGTAIL_DATE_FORMAT`` setting with fallback to '%Y-%m-%d'.
+    :param format: Date format. This must be one of the recognized formats listed in the :std:setting:`django:DATE_INPUT_FORMATS` setting. If not specified Wagtail will use the ``WAGTAIL_DATE_FORMAT`` setting with fallback to ``"%Y-%m-%d"``.
     :param required: If true (the default), the field cannot be left blank.
     :param help_text: Help text to display alongside the field.
     :param validators: A list of validation functions for the field (see :doc:`Django Validators <django:ref/validators>`).
@@ -201,6 +201,7 @@ All block definitions accept the following optional keyword arguments:
 
     A time picker. The following keyword arguments are accepted in addition to the standard ones:
 
+    :param format: Time format. This must be one of the recognized formats listed in the :std:setting:`django:TIME_INPUT_FORMATS` setting. If not specified Wagtail will use the ``WAGTAIL_TIME_FORMAT`` setting with fallback to ``"%H:%M"``.
     :param required: If true (the default), the field cannot be left blank.
     :param help_text: Help text to display alongside the field.
     :param validators: A list of validation functions for the field (see :doc:`Django Validators <django:ref/validators>`).
@@ -212,7 +213,7 @@ All block definitions accept the following optional keyword arguments:
 
     A combined date/time picker. The following keyword arguments are accepted in addition to the standard ones:
 
-    :param format: Date/time format. This must be one of the recognized formats listed in the `DATETIME_INPUT_FORMATS <https://docs.djangoproject.com/en/stable/ref/settings/#std:setting-DATETIME_INPUT_FORMATS>`_ setting. If not specified Wagtail will use the ``WAGTAIL_DATETIME_FORMAT`` setting with fallback to '%Y-%m-%d %H:%M'.
+    :param format: Date/time format. This must be one of the recognized formats listed in the :std:setting:`django:DATETIME_INPUT_FORMATS` setting. If not specified Wagtail will use the ``WAGTAIL_DATETIME_FORMAT`` setting with fallback to ``"%Y-%m-%d %H:%M"``.
     :param required: If true (the default), the field cannot be left blank.
     :param help_text: Help text to display alongside the field.
     :param validators: A list of validation functions for the field (see :doc:`Django Validators <django:ref/validators>`).