Use environment variables for configuration in developer tooling

Avoid the need for configuration files for temporary database connections.

test/Main.hs

@@ -57,7 +57,7 @@ main :: IO ()
 main = do
   getTime <- mkAutoUpdate defaultUpdateSettings { updateAction = getCurrentTime }
 
-  testDbConn <- getEnvVarWithDefault "POSTGREST_TEST_CONNECTION" "postgres://postgrest_test@localhost/postgrest_test"
+  testDbConn <- getEnvVarWithDefault "PGRST_DB_URI" "postgres://postgrest_test@localhost/postgrest_test"
 
   pool <- P.acquire (3, 10, toS testDbConn)