[WIP] [Bug]: App files to compile if DATABASE_URL is not set (#62)

* Initial plan

* Fix: provide fallback DATABASE_URL for dev and test environments

Co-authored-by: maxneuvians <867334+maxneuvians@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: maxneuvians <867334+maxneuvians@users.noreply.github.com>

Author: Copilot

valentine/config/dev.exs

@@ -2,7 +2,8 @@ import Config
 
 # Configure your database
 config :valentine, Valentine.Repo,
-  url: System.get_env("DATABASE_URL") <> "/valentine_dev",
+  url:
+    (System.get_env("DATABASE_URL") || "ecto://postgres:postgres@localhost") <> "/valentine_dev",
   stacktrace: true,
   show_sensitive_data_on_connection_error: true,
   pool_size: 10

valentine/config/test.exs

@@ -6,7 +6,9 @@ import Config
 # to provide built-in test partitioning in CI environment.
 # Run `mix help test` for more information.
 config :valentine, Valentine.Repo,
-  url: System.get_env("DATABASE_URL") <> "/valentine_test#{System.get_env("MIX_TEST_PARTITION")}",
+  url:
+    (System.get_env("DATABASE_URL") || "ecto://postgres:postgres@localhost") <>
+      "/valentine_test#{System.get_env("MIX_TEST_PARTITION")}",
   pool: Ecto.Adapters.SQL.Sandbox,
   pool_size: System.schedulers_online() * 2