CONTRIBUTING: note about copyright line, test credentials expiring

Author: UweTrottmann

CONTRIBUTING.md

@@ -8,7 +8,9 @@ If you contribute any [non-trivial](http://www.gnu.org/prep/maintain/maintain.ht
 Keep your pull requests small, otherwise it is less likely they will get merged.
 
 1. [Fork trakt-java](https://github.com/UweTrottmann/trakt-java/fork).
-2. Create a new branch and make [great commits + messages](http://robots.thoughtbot.com/post/48933156625/5-useful-tips-for-a-better-commit-message). If you add or modify endpoints, make sure to also create and run basic tests (see `src/test`).
+2. Create a new branch and make [great commits](http://robots.thoughtbot.com/post/48933156625/5-useful-tips-for-a-better-commit-message).
+   - If you add or modify endpoints, make sure to also create and run basic tests (see `src/test`).
+   - If you make non-trivial changes (see above), make sure to add a copyright line at the top of the file. 
 3. [Start a pull request](https://github.com/UweTrottmann/trakt-java/compare) against `main`.
 
 #### No code!
@@ -17,3 +19,7 @@ Keep your pull requests small, otherwise it is less likely they will get merged.
 ## Setup
 
 This project is built with [Maven](https://maven.apache.org/), see the `pom.xml` in the root folder.
+
+The tests provide temporary credentials (see [BaseTestCase](src/test/java/com/uwetrottmann/trakt5/BaseTestCase.java)),
+so running tests should just work.
+If an unauthorized error is returned, let me know that the test credentials need to be refreshed.