feat: update emails with branding template

[minh-biocommons]

Description

AAI-786: Templates on emails send from aai-backend

Update emails with branding

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have added unit / integration tests that prove my fix is effective or that my feature works
• I have run all tests locally and they pass
• I have updated the documentation (if applicable)
• For any new secrets, I have updated the shared spreadsheet and the GitHub Secrets.

Screenshots

[amandazhuyilan]

Hi @minh-biocommons do you mind putting up some screenshots for the updated emails - thanks!

[amandazhuyilan]

Thanks @minh-biocommons - for consistency, do we want to all add the black button "Go to BioCommons Access Portal" instead of the url link to 'please visit the "BioCommons Access Portal"' in the emails (ex: notification emial for username update, Confirm updated email, notification email for email update)

[amandazhuyilan]

Sorry for leaving this open for so long! Good to go