[WPB-27953] SCIM: advertise all schemas used in User (fixes RFC compliance issue).

[fisx]

Fixes #5436

This can only be an issue for a user if they look at the "schemas" field of a SCIM user and require that it contains false information. (No need to make this a release notes topic in the changelog.)

$ curl http://localhost:8088/scim/v2/ResourceTypes | jq .
{
  "Resources": [
    {
      "endpoint": "/Users",
      "name": "User",
      "schema": "urn:ietf:params:scim:schemas:core:2.0:User",
      "schemaExtensions": [
        {
          "required": false,
          "schema": "urn:wire:scim:schemas:profile:1.0"
        },
        {
          "required": false,
          "schema": "urn:ietf:params:scim:schemas:extension:wire:1.0:User"
        }
      ]
    },
    {
      "endpoint": "/Groups",
      "name": "Group",
      "schema": "urn:ietf:params:scim:schemas:core:2.0:Group"
    }
  ],
  "itemsPerPage": 2,
  "schemas": [
    "urn:ietf:params:scim:api:messages:2.0:ListResponse"
  ],
  "startIndex": 1,
  "totalResults": 2
}

https://wearezeta.atlassian.net/browse/WPB-27953

Checklist

• Add a new entry in an appropriate subdirectory of changelog.d
• Read and follow the PR guidelines