fix(users): Check lineage across entities in invite

[ThisIsMani]

[## Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

Currently in invites we don't check if user exists across entities.
This will be a problem when inviting a user with higher entity from different lineage.
This PR fixes it.
Main PR: #6677

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

Closes #6679

How did you test it?

1. Invite a user in a specific (org, merchant, profile) combination.
2. Create a new profile in the same merchant account and switch to it.
3. Invite the same user as merchant level user. This should be stopped by API.

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible

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Changed Files

File	Status
crates/router/src/core/user.rs	0% smaller