[fix] resolve email case sensitivity causing 401 authentication errors

[Rohitkhapre]

• Fix case sensitivity mismatch between agenta_oss_core and agenta_oss_supertokens databases
• SuperTokens normalizes emails to lowercase during signup/login
• Agenta was storing emails with original case from invitations
• This caused 401 errors when users tried to login with mixed case emails

Changes:

• Make get_user_with_email() case-insensitive using func.lower()
• Make all invitation-related email lookups case-insensitive
• Normalize emails to lowercase when creating invitations
• Normalize emails in create_accounts() function
• Add comprehensive test to verify the fix

Fixes #2880

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[junaway]

Hi @Rohitkhapre,

Thank you for you contribution!

Normalizing inbound email values is definitely a good idea.
Adding normalization to database queries, less so.

After this PR, we must assume that email values will be normalized once they enter our API, and thus our database.
Otherwise it is very likely that, in the future, this issue creeps in again, in a different place, because of already-corrupted data.

What I suggest is, let's:

• keep normalization in API endpoints
• remove normalization in database queries
• fix corrupted data in the database (either manually or by adding a clean omnipotent data migration)

What do you think ?
Do you feel like giving it a try ?