Add CI for synapse_port_db (#6140)

This adds:

* a test sqlite database
* a configuration file for the sqlite database
* a configuration file for a postgresql database (using the credentials in `.buildkite/docker-compose.pyXX.pgXX.yaml`)

as well as a new script named `.buildkite/scripts/test_synapse_port_db.sh` that:

1. installs Synapse
2. updates the test sqlite database to the latest schema and runs background updates on it
3. creates an empty postgresql database
4. run the `synapse_port_db` script to migrate the test sqlite database to the empty postgresql database (with coverage)

Step `2` is done via a new script located at `scripts-dev/update_database`.

The test sqlite database is extracted from a SyTest run, so that it can be considered as an actual homeserver's database with actual data in it.

1 files changed, 6 insertions, 3 deletions

diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py

index 80b57a948c..37d469ffd7 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -94,13 +94,16 @@ class BackgroundUpdateStore(SQLBaseStore):
         self._all_done = False
 
     def start_doing_background_updates(self):
-        run_as_background_process("background_updates", self._run_background_updates)
+        run_as_background_process("background_updates", self.run_background_updates)
 
     @defer.inlineCallbacks
-    def _run_background_updates(self):
+    def run_background_updates(self, sleep=True):
         logger.info("Starting background schema updates")
         while True:
-            yield self.hs.get_clock().sleep(self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0)
+            if sleep:
+                yield self.hs.get_clock().sleep(
+                    self.BACKGROUND_UPDATE_INTERVAL_MS / 1000.0
+                )
 
             try:
                 result = yield self.do_next_background_update(