feat: control default services via env vars

Read default postgres compose service name and default django compose
service name from env variables.

AHAB_POSTGRES_CONTAINER - defaults to `appserver`
AHAB_DJANGO_CONATINER - defaults to `postgresdb`

Default values are there for 100% backwards compatibility.

src/main.rs

@@ -36,9 +36,13 @@ fn main() -> Result<()> {
             cli::Django::Shell => scripts::django::shell(),
             cli::Django::Test => scripts::django::test(),
         },
-        cli::Commands::Postgres { command } => match command {
-            cli::Postgres::Import { path } => scripts::postgres::import(&path),
-            cli::Postgres::Dump { path } => scripts::postgres::dump(&path),
-        },
+        cli::Commands::Postgres { command } => {
+            let db_container =
+                std::env::var("AHAB_POSTGRES_CONTAINER").unwrap_or("postgresdb".to_string());
+            match command {
+                cli::Postgres::Import { path } => scripts::postgres::import(&db_container, &path),
+                cli::Postgres::Dump { path } => scripts::postgres::dump(&db_container, &path),
+            }
+        }
     }
 }