Add Postgres and MySQL databases support (#335)

docs/configuration/databases/sqlite.md

@@ -0,0 +1,39 @@
+# Using SQLite
+
+By default, Opengist uses SQLite as the database backend.
+
+Because SQLite is a file-based database, there is not much configuration to tweak.
+
+The configuration `db-uri`/`OG_DB_URI` refers to the path of the SQLite database file relative in the `$opengist-home/` directory (default `opengist.db`),
+although it can be left untouched.
+
+The SQLite journal mode is set to [`WAL` (Write-Ahead Logging)](https://www.sqlite.org/pragma.html#pragma_journal_mode) by default and can be changed.
+
+#### YAML
+```yaml
+sqlite.journal-mode: WAL
+```
+
+#### Environment variable
+```sh
+OG_SQLITE_JOURNAL_MODE=WAL
+```
+
+### Docker Compose
+```yml
+version: "3"
+
+services:
+  opengist:
+    image: ghcr.io/thomiceli/opengist:1
+    container_name: opengist
+    restart: unless-stopped
+    ports:
+      - "6157:6157" # HTTP port
+      - "2222:2222" # SSH port, can be removed if you don't use SSH
+    volumes:
+      - "$HOME/.opengist:/opengist"
+    environment:
+      OG_SQLITE_JOURNAL_MODE: WAL
+      # other configuration options
+```