feat: Adding redirection changes for enterprise users (#134)

[subhashree-sahu31]

• feat: Adding redirection changes for enterprise users

• fix: removed request from the waffle flag arguements

(cherry picked from commit 2e2ea9a)

Description
This PR backports edx/edx-platform PR #134 to openedx/openedx-platform:master.

It updates logistration redirect behavior for users hitting the legacy Django login/registration page when the AuthN MFE redirect path is enabled.

Changes included in this backport:

Adds a new waffle flag: user_authn.enable_enterprise_redirect_to_authn
Allows Enterprise/B2B users to be redirected to the AuthN MFE only when that flag is enabled
Keeps B2C users eligible for AuthN MFE redirect by default, as before
Prevents redirect to the AuthN MFE for flows involving external auth providers such as SAML or other TPA-based login
Preserves the legacy Django login flow for Enterprise users unless explicitly opted in via the new flag

Impacted user roles:

Learner: affected, because login and registration entry behavior can change depending on user segment and authentication setup
Operator: affected, because rollout is controlled through a waffle flag and needs operational awareness
Developer: affected, because login redirect behavior is now segmented for Enterprise vs B2C users
Implications for consumers of this change:

Enterprise customers can be migrated to the AuthN MFE incrementally instead of all at once
Enterprise customers using external auth providers remain on the legacy flow
Operators must enable the new waffle flag deliberately for Enterprise rollout
B2C users continue to follow the MFE redirect path when the global AuthN redirect setting is enabled

Supporting information
Original PR: https://github.com/edx/pull/134

Original merge commit: 2e2ea9a

This is a backport from edx/edx-platform/release-ulmo into openedx/openedx-platform:master.

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[mphilbrick211]

Hi @subhashree-sahu31! Welcome, and thank you for this contribution! In order for your CLA check to turn green, you'll need to submit a CLA form. If you are contributing as an individual, please fill out the individual CLA form here.

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Please let me know if you have any questions. Thanks!