Refs #12990 -- Added DatabaseFeatures.has_json_operators.

CockroachDB also has them.

django/db/backends/base/features.py

@@ -309,6 +309,8 @@ class BaseDatabaseFeatures:
     supports_primitives_in_json_field = True
     # Is there a true datatype for JSON?
     has_native_json_field = False
+    # Does the backend use PostgreSQL-style JSON operators like '->'?
+    has_json_operators = False
 
     def __init__(self, connection):
         self.connection = connection

django/db/backends/postgresql/features.py

@@ -58,6 +58,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supported_explain_formats = {'JSON', 'TEXT', 'XML', 'YAML'}
     validates_explain_options = False  # A query will error on invalid options.
     supports_deferrable_unique_constraints = True
+    has_json_operators = True
 
     @cached_property
     def is_postgresql_10(self):