feat(calendar): Readded support for multiple groups and made it more integrated + avoided blocked groups

[lwcorp]

Description

1. Undid the removal of the support for multiple groups (why did you allow this person's PR just so they fix formatting?)
2. Made the multiple groups and get all members functions to use each other to avoid duplicated code
3. Added support for avoiding blocked groups (e.g. external ones)
4. Simplified both functions' code

Is it been tested?

• [X ] Development testing done

Checklist

• [X ] My code follows the style guidelines of this project
• [X ] I have performed a self-review of my own code
• [X ] I have performed a peer-reviewed with team member(s)
• [X ] I have commented my code, particularly in hard-to-understand areas
• [X ] I have made corresponding changes to the documentation
• [X ] My changes generate no new warnings
• [X ] Any dependent changes have been merged and published in downstream modules

[conventional-commit-lint-gcf]

🤖 I detect that the PR title and the commit message differ and there's only one commit. To use the PR title for the commit history, you can use Github's automerge feature with squashing, or use automerge label. Good luck human!

-- conventional-commit-lint bot
https://conventionalcommits.org/

[lwcorp]

Merged with #456.