Add ability to pass redis hostname as env var (#174)

* Add ability to pass redis hostname as env var

* Read postgres host from env var in microservices

* Update .env.example with postgres and redis hostname vars

microservices/src/config/database.config.ts

@@ -2,7 +2,7 @@ import { TypeOrmModuleOptions } from '@nestjs/typeorm';
 
 export const databaseConfig: TypeOrmModuleOptions = {
   type: 'postgres',
-  host: 'immich_postgres',
+  host: process.env.DB_HOSTNAME || 'immich_postgres',
   port: 5432,
   username: process.env.DB_USERNAME,
   password: process.env.DB_PASSWORD,