Add documentation for age verification (#1613)

content/en/entities/Instance.md

@@ -121,7 +121,8 @@ aliases: [
   "registrations": {
     "enabled": false,
     "approval_required": false,
-    "message": null
+    "message": null,
+    "min_age": 16
   },
   "api_versions": {
     "mastodon": 1,
@@ -511,6 +512,13 @@ aliases: [
 **Version history:**\
 4.0.0 - added
 
+#### `registrations[min_age]` {#registrations-min_age}
+
+**Description:** A minimum age required to register, if configured.\
+**Type:** {{<nullable>}} Integer or null\
+**Version history:**\
+4.4.0 - added
+
 ### `api_versions` {#api-versions}
 
 **Description:** Information about which version of the API is implemented by this server. It contains at least a `mastodon` attribute, and other implementations may have their own additional attributes.\

content/en/methods/accounts.md

@@ -32,7 +32,8 @@ A relationship between the OAuth Application and created user account is stored.
 **Version history:**\
 2.7.0 - added\
 3.0.0 - added `reason` parameter\
-3.4.0 - added `details` to failure response
+3.4.0 - added `details` to failure response\
+4.4.0 - added `date_of_birth` parameter
 
 #### Request
 
@@ -61,6 +62,9 @@ locale
 reason
 : String. If registrations require manual approval, this text will be reviewed by moderators.
 
+date_of_birth
+: String ([Date](/api/datetime-format#date)), required if the server has a minimum age requirement.
+
 #### Response
 
 ##### 200: OK