"Add Collection" form loads

[alisaismailati]

References

• Replaces Fix "Edit -> Collection" by restoring ngOnInit() method which was accidentally removed #2329
• Fixes Collection creation page is not rendered DSpace#8911

Description

ngOnInit() is implemented for collection-form.component.ts .

Instructions for Reviewers

List of changes in this PR:

• First, the ngOnInit() is implemented for src/app/collection-page/collection-form/collection-form.component.ts. When a collection is edited, ngOnChanges is called before ngOnInit, so on ngOnInit we need to check if the formModel is already initialized and if it is not, we need to initialize it. We also need to check the dso to be different from null in order to initialize the form.

Include guidance for how to test or review your PR.
Steps to reproduce a bug are the same as mentioned in #2329.

Checklist

• My PR is small in size (e.g. less than 1,000 lines of code, not including comments & specs/tests), or I have provided reasons as to why that's not possible.
• My PR passes ESLint validation using yarn lint
• My PR doesn't introduce circular dependencies (verified via yarn check-circ-deps)
• My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• If my PR includes new libraries/dependencies (in package.json), I've made sure their licenses align with the DSpace BSD License based on the Licensing of Contributions documentation.
• If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• If my PR fixes an issue ticket, I've linked them together.

[tdonohue]

👍 Thanks @alisaismailati ! This looks good to me & it works