User Invitation can allow uppercase email to login

[KoWeiJAC]

Is your feature request related to a problem? Please describe.
If send User Invitation with emails contain uppercase, user can not login with this email,
Admin will show the error message You have not been invited to use this site. Please contact the Digital Team for assistance..The invitation store email with uppercase, the system will query the email with all lowercase, so can the invitation will not be found.

Describe the solution you'd like
System can query and store emails in all lowercase.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.