Removed observable function calls from template (part 1)

[alexandrevryghem]

References

• Fixes #3393
• Fixes #3257
• Fixes #3571

Description

Currently, there are multiple instances where observable function calls are subscribed to directly in the template. This is considered a bad practice, as it cause a new Observable to be recreated each time Angular’s change detection is triggered. Some instances of this issue remain, but I will work on creating PRs to address them over the coming months.

Instructions for Reviewers

Guidance for how to test & review this PR:

• Verify that the 3 linked issues have been resolved
• Verify that all these functionalities still work correctly:
  • EPerson pages
  • Group pages
  • Bitstream Format Registry
  • Metadata Registry
  • A component that uses the pagination component

Checklist

• [x] My PR is created against the main branch of code (unless it is a backport or is fixing an issue specific to an older branch).
• [x] 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.
• [x] My PR passes ESLint validation using npm run lint
• [x] My PR doesn't introduce circular dependencies (verified via npm run check-circ-deps)
• [x] My PR includes TypeDoc comments for all new (or modified) public methods and classes. It also includes TypeDoc for large or complex private methods.
• [x] My PR passes all specs/tests and includes new/updated specs or tests based on the Code Testing Guide.
• [x] My PR aligns with Accessibility guidelines if it makes changes to the user interface.
• [x] My PR uses i18n (internationalization) keys instead of hardcoded English text, to allow for translations.
• [x] My PR includes details on how to test it. I've provided clear instructions to reviewers on how to successfully test this fix or feature.
• [x] 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.
• [x] If my PR includes new features or configurations, I've provided basic technical documentation in the PR itself.
• [x] If my PR fixes an issue ticket, I've linked them together.