Clarify formats of string types in account sections

changelogs/client_server/newsfragments/2046.clarification

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

data/api/client-server/registration.yaml

@@ -135,6 +135,8 @@ paths:
                 properties:
                   user_id:
                     type: string
+                    format: mx-user-id
+                    pattern: "^@"
                     description: |-
                       The fully-qualified Matrix user ID (MXID) that has been registered.
 
@@ -169,6 +171,7 @@ paths:
                     x-addedInMatrixVersion: "1.3"
                   home_server:
                     type: string
+                    format: mx-server-name
                     deprecated: true
                     description: |-
                       The server_name of the homeserver on which the account has

data/api/client-server/whoami.yaml

@@ -44,6 +44,8 @@ paths:
                 properties:
                   user_id:
                     type: string
+                    format: mx-user-id
+                    pattern: "^@"
                     description: The user ID that owns the access token.
                   device_id:
                     x-addedInMatrixVersion: "1.1"

data/api/identity/definitions/request_email_validation.yaml

@@ -23,6 +23,7 @@ properties:
     example: "monkeys_are_GREAT"
   email:
     type: string
+    format: email
     description: The email address to validate.
     example: "[email protected]"
   send_attempt:
@@ -39,6 +40,7 @@ properties:
     example: 1
   next_link:
     type: string
+    format: uri
     description: |-
       Optional. When the validation is completed, the identity server will
       redirect the user to this URL. This option is ignored when submitting

data/api/identity/definitions/request_msisdn_validation.yaml

@@ -44,6 +44,7 @@ properties:
     example: 1
   next_link:
     type: string
+    format: uri
     description: |-
       Optional. When the validation is completed, the identity server will
       redirect the user to this URL. This option is ignored when submitting

data/event-schemas/schema/m.identity_server.yaml

@@ -9,7 +9,10 @@ properties:
     type: object
     properties:
       base_url:
-        type: string
+        anyOf:
+          - type: string
+            format: uri
+          - type: "null"
         description: |-
           The URL of the identity server the user prefers to use, or `null`
           if the user does not want to use an identity server. This value is