Add Postgres and MySQL databases support (#335)

docs/configuration/databases/mysql.md

@@ -0,0 +1,49 @@
+# Using MySQL/MariaDB
+
+To use MySQL/MariaDB as the database backend, you need to set the database URI configuration to the connection string of your MySQL/MariaDB database with this format :
+
+`mysql://<user>:<password>@<host>:<port>/<database>`
+
+#### YAML
+```yaml
+# Example
+db-uri: mysql://root:passwd@localhost:3306/opengist_db
+```
+
+#### Environment variable
+```sh
+# Example
+OG_DB_URI=mysql://root:passwd@localhost:3306/opengist_db
+```
+
+### Docker Compose
+```yml
+version: "3"
+
+services:
+  opengist:
+    image: ghcr.io/thomiceli/opengist:1
+    container_name: opengist
+    restart: unless-stopped
+    depends_on:
+      - mysql
+    ports:
+      - "6157:6157"
+      - "2222:2222"
+    volumes:
+      - "$HOME/.opengist:/opengist"
+    environment:
+      OG_DB_URI: mysql://opengist:secret@mysql:3306/opengist_db
+      # other configuration options
+
+  mysql:
+    image: mysql:8.4
+    restart: unless-stopped
+    volumes:
+      - "./opengist-database:/var/lib/mysql"
+    environment:
+      MYSQL_USER: opengist
+      MYSQL_PASSWORD: secret
+      MYSQL_DATABASE: opengist_db
+      MYSQL_ROOT_PASSWORD: rootsecret
+```