feat(api): An order_by param for user.ListMyRepos

Add an optional `order_by` parameter to the `user.ListMyRepos`
handler (which handles the `/api/v1/user/repos` route), allowing a user
to sort repos by name (the default), id, or size.

The latter will be useful later for figuring out which repos use most
space, which repos eat most into a user's quota.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

templates/swagger/v1_json.tmpl

@@ -17529,11 +17529,20 @@
             "description": "page size of results",
             "name": "limit",
             "in": "query"
+          },
+          {
+            "type": "string",
+            "description": "order the repositories by name (default), id, or size",
+            "name": "order_by",
+            "in": "query"
           }
         ],
         "responses": {
           "200": {
             "$ref": "#/responses/RepositoryList"
+          },
+          "422": {
+            "$ref": "#/responses/validationError"
           }
         }
       },