Issue:
Bug: bug(users): Check lineage across entities in invite



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.
We should check if user exists across lineage before allowing invite in this case.



Pull request description:
## Type of Change
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- [x] Bugfix
- [ ] New feature
- [ ] Enhancement
- [ ] Refactoring
- [ ] Dependency updates
- [ ] Documentation
- [ ] CI/CD

## Description
<!-- Describe your changes in detail -->
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.

### Additional Changes

- [ ] This PR modifies the API contract
- [ ] This PR modifies the database schema
- [ ] This PR modifies application configuration/environment variables

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Following are the paths where you can find config files:
1. `config`
2. `crates/router/src/configs`
3. `loadtest/config`
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## Motivation and Context
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that will have little conversation).
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Closes #6679.

## How did you test it?
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Did you write an integration/unit/API test to verify the code changes?
Or did you test this change manually (provide relevant screenshots)?
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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
<!-- Put an `x` in the boxes that apply -->

- [x] I formatted the code `cargo +nightly fmt --all`
- [x] I addressed lints thrown by `cargo clippy`
- [x] I reviewed the submitted code
- [ ] I added unit tests for my changes where possible


Testing:

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.

Patch:
diff --git a/crates/router/src/core/user.rs b/crates/router/src/core/user.rs
index c6501dac3bd..2087d01dbb4 100644
--- a/crates/router/src/core/user.rs
+++ b/crates/router/src/core/user.rs
@@ -642,6 +642,38 @@ async fn handle_existing_user_invitation(
         return Err(UserErrors::UserExists.into());
     }
 
+    let (org_id, merchant_id, profile_id) = match role_info.get_entity_type() {
+        EntityType::Organization => (Some(&user_from_token.org_id), None, None),
+        EntityType::Merchant => (
+            Some(&user_from_token.org_id),
+            Some(&user_from_token.merchant_id),
+            None,
+        ),
+        EntityType::Profile => (
+            Some(&user_from_token.org_id),
+            Some(&user_from_token.merchant_id),
+            Some(&user_from_token.profile_id),
+        ),
+    };
+
+    if state
+        .global_store
+        .list_user_roles_by_user_id(ListUserRolesByUserIdPayload {
+            user_id: invitee_user_from_db.get_user_id(),
+            org_id,
+            merchant_id,
+            profile_id,
+            entity_id: None,
+            version: None,
+            status: None,
+            limit: Some(1),
+        })
+        .await
+        .is_ok_and(|data| data.is_empty().not())
+    {
+        return Err(UserErrors::UserExists.into());
+    }
+
     let user_role = domain::NewUserRole {
         user_id: invitee_user_from_db.get_user_id().to_owned(),
         role_id: request.role_id.clone(),