feat: add LDAP authentication module with JWT issuance

[mundele2004]

Pull Request Template

Description:

• Added a plug-and-play LDAP authentication module under internal/auth/ldapauth.
• The module performs Bind(username, password) authentication against an LDAP server and issues a JWT token upon successful login.
• Addresses the LDAP Integration proposal for GoFr Framework Extension as per SOC.
• Closes: issue [GoFr-SOC]: LDAP Integration Helper Module #2014

Breaking Changes (if applicable):

• None. This module is self-contained and does not interfere with any existing authentication mechanisms or routing middleware.

Additional Information:

• External Library used: github.com/go-ldap/ldap/v3
• JWT is issued using standard library packages (crypto/rand, encoding/base64) with HMAC SHA256 signing.
• Unit tests include edge cases using a mock LDAP dialer function.
• See mainFile/main.go for demo and testuser.ldif for testing against a local OpenLDAP instance.
• Sample test user:

Summary

This PR introduces a standalone LDAP authentication module (internal/auth/ldapauth) for the GoFr framework. It uses Bind(username, password) to validate users and issues a JWT on successful login.

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What's Included

• ldapauth.go: Core logic for LDAP authentication and JWT issuance
• ldapauth_test.go: Unit tests with mock LDAP dialer
• main.go: Demo login flow using /login route
• testuser.ldif: Sample LDAP user for testing

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How to Test

1. Run local LDAP server (e.g., using Docker: osixia/openldap)
2. Load test user using testuser.ldif:

   docker cp mainFile/testuser.ldif myldap:/testuser.ldif
   docker exec -it myldap ldapadd -x -D "cn=admin,dc=example,dc=com" -w admin -f /testuser.ldif

3. Run the server:- go run mainFile/main.go
4. Test login:
   curl -X POST http://localhost:8080/login
   -H "Content-Type: application/json"
   -d '{"username":"testuser", "password":"testpass"}'

Checklist:

• I have formatted my code using goimport and golangci-lint.
• All new code is covered by unit tests.
• This PR does not decrease the overall code coverage.
• I have reviewed the code comments and documentation for clarity.