Signed-off-by: Stephanie yangcao@redhat.com

What does this PR do?

This PR updates add apis to process everything before return an error.
The error returned is a total error which contains error of all invalid elements during that add action

What issues does this PR fix or reference?

Fixes devfile/api#449

Is your PR tested? Consider putting some instruction how to test your changes

update unit tests to check for error message