Added API for Limits

Change-Id: I523c4d747ac42bac56147ec9324f5e7f45df7e9b

openstack-database-api/src/markdown/database-api-v1.md

@@ -468,7 +468,75 @@ Example entity:
         }
     }
 
+### Limits: `/v1/limits`
 
+Database-as-a-Service supports API rate limiting for its API. The rate limiting
+allows an administrator to configure limits on the type and number of API calls
+that can be made in a specific time interval. DBaaS also supports absolute
+limits. An admin can configure and impose absolute limits on resources consumed
+by users.
+
+When API rate limits are exceeded, HTTP requests will return a error with a
+status code of 413 "Request entity too large", and will also include a
+'Retry-After' HTTP header. The response body will include the error details,
+and the delay before the request should be retried. Rate limits are applied in
+order, relative to the HTTP method, going from least to most specific.
+
+Absolute limits are specified as name/value pairs. The name of the absolute
+limit uniquely identifies the limit within a deployment. Please consult your
+provider for an exhaustive list of absolute value names. An absolute limit value
+is always specified as an integer. The name of the absolute limit determines the
+unit type of the integer value. For example, the name max_instances implies that
+the value is in terms of number of instances.
+
+Example entity:
+
+     {
+        "limits": [
+            {
+                "max_instances": 10,
+                "max_volumes": 100,
+                "max_backups": 20,
+                "verb": "ABSOLUTE"
+            },
+            {
+                "nextAvailable": "2013-05-21T17:27:25Z",
+                "regex": ".*",
+                "remaining": 200,
+                "unit": "MINUTE",
+                "uri": "*",
+                "value": 200,
+                "verb": "POST"
+            },
+            {
+                "nextAvailable": "2013-05-21T17:27:25Z",
+                "regex": ".*",
+                "remaining": 200,
+                "unit": "MINUTE",
+                "uri": "*",
+                "value": 200,
+                "verb": "PUT"
+            },
+            {
+                "nextAvailable": "2013-05-21T17:27:25Z",
+                "regex": ".*",
+                "remaining": 200,
+                "unit": "MINUTE",
+                "uri": "*",
+                "value": 200,
+                "verb": "DELETE"
+            },
+            {
+                "nextAvailable": "2013-05-21T17:27:25Z",
+                "regex": ".*",
+                "remaining": 199,
+                "unit": "MINUTE",
+                "uri": "*",
+                "value": 200,
+                "verb": "GET"
+            }
+            ]
+        }
 
 ### Security Groups: `/v1/security-groups`