docker image: variable for database location and database passord

[dmrzh]

To simplify setting up the server, you need to create environment variables that point to the database.

Аs an example

version: '3.7'
services:
cells:
image: pydio/cells:latest
restart: unless-stopped
ports:
- "8200:8080"
environment:
- CELLS_INSTALL_YAML=/pydio/config/install.yml
- DATABASE_NAME=cells
- DATABASE_HOST=mysql
- DATABASE_PASSWIRD=ChangeMe!
volumes:
- ./cellsdir:/var/cells
- ./install-conf.yml:/pydio/config/install.yml:ro

mysql:
image: mariadb
restart: unless-stopped
environment:
MYSQL_ROOT_PASSWORD: ChangeMe!
MYSQL_DATABASE: cells
MYSQL_USER: pydio
MYSQL_PASSWORD: ChangeMe!
volumes:
- ./mysqldir:/var/lib/mysql