Clarify formats of string types for the GET /.well-known/matrix/support endpoint

changelogs/client_server/newsfragments/1978.clarification

@@ -0,0 +1 @@
+Clarify formats of string types.

data/api/client-server/support.yaml

@@ -54,6 +54,8 @@ paths:
                       properties:
                         matrix_id:
                           type: string
+                          format: mx-user-id
+                          pattern: "^@"
                           description: |-
                             A [Matrix User ID](/appendices/#user-identifiers)
                             representing the administrator.
@@ -66,6 +68,7 @@ paths:
                             required.
                         email_address:
                           type: string
+                          format: email
                           description: |-
                             An email address to reach the administrator.
 
@@ -95,6 +98,7 @@ paths:
                       }
                   support_page:
                     type: string
+                    format: uri
                     description: |-
                       The URL of a page to give users help specific to the
                       homeserver, like extra login/registration steps.

data/custom-formats.yaml

@@ -50,4 +50,7 @@ mx-mxc-uri:
 uri:
   title: URI
   url: http://tools.ietf.org/html/rfc3986
-  # no regex
+
+email:
+  title: Email Address
+  url: https://datatracker.ietf.org/doc/html/rfc5321#section-4.1.2