Update api-ref for unified limits

This patch did:
1. Change the empty string "" to null for `description` property
2. Add the missing `project_id` property back.
3. Add `project_id` filter for listing limits
4. Add `include_limits` filter for showing project

Change-Id: Iffaec737739a29ff81e10f7db33abfc3181fdbbe

api-ref/source/v3/parameters.yaml

@@ -193,6 +193,13 @@ idp_id_query:
   in: query
   required: false
   type: string
+include_limits:
+  description: |
+    It should be used together with `parents_as_list` or `subtree_as_list`
+    filter to add the related project's limits into the response body.
+  in: query
+  required: false
+  type: key-only, no value expected
 include_names_query:
   description: |
     If set to true, then the names of any entities returned will be include as

api-ref/source/v3/projects.inc

@@ -194,6 +194,7 @@ Parameters
    - subtree_as_list: subtree_as_list
    - parents_as_ids: parents_as_ids
    - subtree_as_ids: subtree_as_ids
+   - include_limits: include_limits
 
 Response
 --------

api-ref/source/v3/samples/admin/limit-show-response.json

@@ -9,6 +9,6 @@
         "project_id": "3a705b9f56bb439381b43c4fe59dccce",
         "id": "25a04c7a065c430590881c646cdcdd58",
         "resource_limit": 11,
-        "description": ""
+        "description": null
     }
 }

api-ref/source/v3/samples/admin/limits-create-response.json

@@ -22,7 +22,7 @@
             "project_id": "3a705b9f56bb439381b43c4fe59dccce",
             "id": "3229b3849f584faea483d6851f7aab05",
             "resource_limit": 5,
-            "description": ""
+            "description": null
         }
     ]
 }

api-ref/source/v3/samples/admin/limits-list-response.json

@@ -27,7 +27,7 @@
             "project_id": "3a705b9f56bb439381b43c4fe59dccce",
             "id": "3229b3849f584faea483d6851f7aab05",
             "resource_limit": 5,
-            "description": ""
+            "description": null
         }
     ]
 }

api-ref/source/v3/samples/admin/registered-limits-create-response.json

@@ -20,7 +20,7 @@
             "service_id": "9408080f1970482aa0e38bc2d4ea34b7",
             "default_limit": 5,
             "id": "e35a965b2b244209bb0c2b193c55955f",
-            "description": ""
+            "description": null
         }
     ]
 }

api-ref/source/v3/samples/admin/registered-limits-list-response.json

@@ -14,7 +14,7 @@
             "service_id": "9408080f1970482aa0e38bc2d4ea34b7",
             "default_limit": 10,
             "id": "195acb8a093e43e9afb23d6628361e7c",
-            "description": ""
+            "description": null
         },
         {
             "resource_name": "volume",

api-ref/source/v3/unified_limits.inc

@@ -366,6 +366,7 @@ Parameters
    - service_id: service_id_query
    - region_id: region_id_query
    - resource_name: resource_name_query
+   - project_id: scope_project_id_query
 
 
 Response
@@ -425,6 +426,7 @@ Parameters
 .. rest_parameters:: parameters.yaml
 
    - limits: limits
+   - project_id: project_id
    - service_id: service_id_limit
    - region_id: region_id_request_body
    - resource_name: resource_name
@@ -449,6 +451,7 @@ Parameters
 
    - limits: limits
    - id: limit_id
+   - project_id: project_id
    - service_id: service_id_limit
    - region_id: region_id_response_body
    - resource_name: resource_name
@@ -517,6 +520,7 @@ Parameters
 
    - limit: limit
    - id: limit_id
+   - project_id: project_id
    - service_id: service_id_limit
    - region_id: region_id_response_body
    - resource_name: resource_name