Merge pull request 'docs: add rough documentation about obs-portal' (#173) from feat/obs-portal-nachtigall into main

Reviewed-on: pub-solar/infra#173
Reviewed-by: teutat3s <teutat3s@noreply.git.pub.solar>

docs/obs-portal.md

@@ -0,0 +1,32 @@
+# OpenBikeSensor Portal
+
+## Docker Containers
+* portal
+* worker
+* db
+
+
+## Run database migrations
+
+After an upgrade it is sometimes necessary to run database migrations or regenerate tiles.
+
+```
+docker exec -ti obs-portal tools/upgrade.py
+```
+
+## Dump database
+
+Save database dump to `dump.sql` in the current working directory.
+
+```
+docker exec -ti --user postgres obs-portal-db pg_dump obs > dump.sql
+```
+
+## Restore database
+
+Load database dump from `dump.sql` file.
+`obs` database needs to exist before importing the dump.
+
+```
+cat dump.sql | docker exec -ti --user postgres obs-portal-db psql obs
+```