docs: add mutli database backup example

docs/how-tos/encrypt-backup.md

@@ -6,11 +6,12 @@ nav_order: 8
 ---
 # Encrypt backup
 
-The image supports encrypting backups using one of two available methods: GPG with passphrase or GPG with a public key
+The image supports encrypting backups using one of two available methods: GPG with passphrase or GPG with a public key.
 
-## Using GPG passphrase
 
 The image supports encrypting backups using GPG out of the box. In case a `GPG_PASSPHRASE` or `GPG_PUBLIC_KEY` environment variable is set, the backup archive will be encrypted using the given key and saved as a sql.gpg file instead or sql.gz.gpg.
+Suppose you used a GPG public key during the backup process. In that case, you need to decrypt your backup before restoration because decryption using a `GPG private` key is not fully supported.
+
 
 {: .warning }
 To restore an encrypted backup, you need to provide the same GPG passphrase used during backup process.
@@ -33,7 +34,7 @@ Using your private key
 ```shell
 gpg --output database_20240730_044201.sql.gz --decrypt database_20240730_044201.sql.gz.gpg
 ```
-### Backup
+## Using GPG passphrase
 
 ```yml
 services:
@@ -61,3 +62,32 @@ services:
 networks:
   web:
 ```
+
+## Using GPG Public Key
+
+```yml
+services:
+  pg-bkup:
+    # In production, it is advised to lock your image tag to a proper
+    # release version instead of using `latest`.
+    # Check https://github.com/jkaninda/pg-bkup/releases
+    # for a list of available releases.
+    image: jkaninda/pg-bkup
+    container_name: pg-bkup
+    command: backup -d database
+    volumes:
+      - ./backup:/backup
+    environment:
+      - DB_PORT=5432
+      - DB_HOST=postgres
+      - DB_NAME=database
+      - DB_USERNAME=username
+      - DB_PASSWORD=password
+      ## Required to encrypt backup
+      - GPG_PUBLIC_KEY=/config/public_key.asc
+    # pg-bkup container must be connected to the same network with your database
+    networks:
+      - web
+networks:
+  web:
+```

docs/how-tos/mutli-backup.md

@@ -37,4 +37,28 @@ databases:
     user: joplin
     password: password
     path: /s3-path/joplin #For SSH or FTP you need to define the full path (/home/toto/backup/)
+```
+
+## Docker compose file
+
+```yaml
+services:
+  pg-bkup:
+    # In production, it is advised to lock your image tag to a proper
+    # release version instead of using `latest`.
+    # Check https://github.com/jkaninda/pg-bkup/releases
+    # for a list of available releases.
+    image: jkaninda/pg-bkup
+    container_name: pg-bkup
+    command: backup
+    volumes:
+      - ./backup:/backup
+    environment:
+      ## Multi backup config file
+      - BACKUP_CONFIG_FILE=/backup/config.yaml
+    # pg-bkup container must be connected to the same network with your database
+    networks:
+      - web
+networks:
+  web:
 ```