[FIX] Feedback on bulk invite

[aKn1ghtOut]

Checklist

• I have read the Contributing Guide
• I have signed the CLA
• Lint and unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if applicable)
• I have added necessary documentation (if applicable)
• Any dependent changes have been merged and published in downstream modules

Proposed changes (including videos or screenshots)

Resolved structure where no response was being received. Changed from callback to async/await.
Added error in case of empty submission, or if no valid emails were found.

gitIssueBulkInvite-2021-01-24_02.24.08.mp4

Issue(s)

Closes #19021

Steps to test or reproduce

1. Open administration
2. Invite by email addresses
3. Submit invalid or empty email input [ No error ]
4. No feedback at all on submission

Further comments

[aKn1ghtOut]

@dougfabris @ggazzo Please review

[dougfabris]

@aKn1ghtOut Really nice fix, thank you! I think, to be perfect, we should add a UI validation to prevent the user to send a request with the field empty or even an invalid email.

[yash-rajpal]

@dougfabris my PR #20337 already adds the button disable check, Please review that PR for this functionality. Thanks.

[dougfabris]

@yash-rajpal Really nice, thanks for notifying!

[yash-rajpal]

@dougfabris No problem :). Please tell if that PR requires any changes.
Thanks.