Add feature flag description to groups field on user interface

app/graphql/types/user_interface.rb

@@ -61,7 +61,8 @@ module Types
           description: 'Group memberships of the user.'
     field :groups,
           resolver: Resolvers::Users::GroupsResolver,
-          description: 'Groups where the user has access.'
+          description: 'Groups where the user has access. Will always return `null` if ' \
+                       '`paginatable_namespace_drop_down_for_project_creation` feature flag is disabled.'
     field :group_count,
           resolver: Resolvers::Users::GroupCountResolver,
           description: 'Group count for the user.'

doc/api/graphql/reference/index.md

@@ -11105,7 +11105,7 @@ four standard [pagination arguments](#connection-pagination-arguments):
 
 ##### `MergeRequestAssignee.groups`
 
-Groups where the user has access.
+Groups where the user has access. Will always return `null` if `paginatable_namespace_drop_down_for_project_creation` feature flag is disabled.
 
 Returns [`GroupConnection`](#groupconnection).
 
@@ -11351,7 +11351,7 @@ four standard [pagination arguments](#connection-pagination-arguments):
 
 ##### `MergeRequestReviewer.groups`
 
-Groups where the user has access.
+Groups where the user has access. Will always return `null` if `paginatable_namespace_drop_down_for_project_creation` feature flag is disabled.
 
 Returns [`GroupConnection`](#groupconnection).
 
@@ -14260,7 +14260,7 @@ four standard [pagination arguments](#connection-pagination-arguments):
 
 ##### `UserCore.groups`
 
-Groups where the user has access.
+Groups where the user has access. Will always return `null` if `paginatable_namespace_drop_down_for_project_creation` feature flag is disabled.
 
 Returns [`GroupConnection`](#groupconnection).
 
@@ -17253,7 +17253,7 @@ four standard [pagination arguments](#connection-pagination-arguments):
 
 ###### `User.groups`
 
-Groups where the user has access.
+Groups where the user has access. Will always return `null` if `paginatable_namespace_drop_down_for_project_creation` feature flag is disabled.
 
 Returns [`GroupConnection`](#groupconnection).