docs: Update CONTRIBUTING.md with instructions about custom e2e test (#352)

* docs: Need to run task regen_custom

* docs: Mention task re

Co-authored-by: Constantinos Symeonides <[email protected]>

Author: csymeonides-mf

CONTRIBUTING.md

@@ -21,13 +21,14 @@
    auto-reformat the code, check type annotations, run unit tests, check code coverage, and lint the code.
 3. If you're writing a new feature, try to add it to the end to end test.
    1. If adding support for a new OpenAPI feature, add it somewhere in `end_to_end_tests/openapi.json`
-   2. Regenerate the "golden record" with `task regen`. This is a client generated from the OpenAPI document used for end to end testing.
-   3. Check the changes to `end_to_end_tests/golden-record` to confirm only what you intended to change did change and that the changes look correct.
-4. Run the end to end tests with `task e2e`. This will generate a client against `end_to_end_tests/openapi.json` and
-   compare it with `end_to_end_tests/golden-record`. The test will fail if **anything is different**. The end to end
-   test is not included in `task check` as it takes longer to run and doesn't provide very useful feedback in the
-   event of failure. If this test does fail, the easiest way to check what's wrong is to run `task regen` and check
-   the diff of `golden-record`.
+   2. Regenerate the "golden records" with `task regen` and `task regen_custom`. These are clients generated from the OpenAPI document used for end to end testing.
+   3. Check the changes to `end_to_end_tests/golden-record` and `end_to_end_tests/golden-record-custom` to confirm only what you intended to change did change and that the changes look correct.
+4. Run the end to end tests with `task e2e`. This will generate clients against `end_to_end_tests/openapi.json` and
+   compare them with the golden records. The tests will fail if **anything is different**. The end to end
+   tests are not included in `task check` as they take longer to run and don't provide very useful feedback in the
+   event of failure. If an e2e test does fail, the easiest way to check what's wrong is to run `task regen` and/or
+   `task regen_custom` and check the diffs. You can also use `task re` which will run `regen`, `regen_custom` and `e2e`
+   in that order.
 5. Include a summary of your changes in `CHANGELOG.md`. If there isn't an "Unreleased" version in the CHANGELOG yet,
    go ahead and add one.