refactor: rename test files to clarify API-only scope

Rename roasters.rs to roasters_api.rs and roasts.rs to roasts_api.rs
to make it clear these files only test the /api/v1 endpoints, not the
page endpoints.

Co-authored-by: jnsgruk <668505+jnsgruk@users.noreply.github.com>

tests/server/main.rs

@@ -1,3 +1,3 @@
 pub mod helpers;
-pub mod roasters;
-pub mod roasts;
+pub mod roasters_api;
+pub mod roasts_api;