Document 409 Conflict responses that can be returned for any REST endpoint

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I8a237c4f2c4348460d2bfacb788c0ee9e395d875
diff --git a/resources/Documentation/rest-api.md b/resources/Documentation/rest-api.md
index 9afd554..22fd38a 100644
--- a/resources/Documentation/rest-api.md
+++ b/resources/Documentation/rest-api.md
@@ -455,6 +455,16 @@
   }
 ```
 
+## <a id="general-responses"> General Responses
+
+All REST endpoints may return the following responses:
+
+* `409 Conflict` is returned if a request cannot be executed due to:
+** an non-parseable code owner config file (in this case the project owners need
+   to fix the code owner config file)
+** an invalid plugin configuration (in this case the project owners need to fix
+   the code-owners plugin configuration)
+
 ## <a id="ids"> IDs
 
 ### <a id="path"> \{path\}