Use join_policy API instead of joinable

The API is now under
 /groups/$group_id/setting/m.join_policy

and expects a JSON blob of the shape

```json
{
  "m.join_policy": {
    "type": "invite"
  }
}
```

where "invite" could alternatively be "open".

1 files changed, 7 insertions, 1 deletions

diff --git a/synapse/storage/schema/delta/48/groups_joinable.sql b/synapse/storage/schema/delta/48/groups_joinable.sql

index ace7d0a723..ab3b00286d 100644
--- a/synapse/storage/schema/delta/48/groups_joinable.sql
+++ b/synapse/storage/schema/delta/48/groups_joinable.sql
@@ -13,4 +13,10 @@
  * limitations under the License.
  */
 
-ALTER TABLE groups ADD COLUMN is_joinable SMALLINT DEFAULT 0 NOT NULL;
+/* 
+ * This isn't a real ENUM because sqlite doesn't support it
+ * and we use a default of NULL for inserted rows and interpret
+ * NULL at the python store level as necessary so that existing
+ * rows are given the correct default policy.
+ */
+ALTER TABLE groups ADD COLUMN join_policy TEXT DEFAULT NULL;