Feat: Add POST endpoint to user application

# Description created a test user to be used for testing later on added questionIds to map questions and responses added an endpoint to submit user application (more information) 1. extract user information like firstname, lastname from user responses 2. create a userApplication table entry 3. update user record ## Issue link https://app.clickup.com/t/86b3uaef0 https://docs.google.com/document/d/19hQx5LAn27XVvh1x4VsREzuX86SOc4PFTeAXRzVZWBE/edit?tab=t.0 ## Type of change - [ ] Bug fix (non-breaking change which fixes an issue) - [ ] Feature updates / changes - [ ] Tests - [x] New feature (non-breaking change which adds functionality) - [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected) - [ ] This change requires a documentation update # How Has This Been Tested? 1. Login with the user who is submitting the application 2. /users/application, copy the sample request body from the description 3. it should have added a new user application and updated user record, and user will have a linked user application 4. run it again with the same user, it should give a 409 error # Checklist: - [x] My code follows the style guidelines of this project - [x] I have performed a self-review of my code - [x] I have commented my code, particularly in hard-to-understand areas - [x] I have made corresponding changes to the documentation - [x] My changes generate no new warnings - [x] I have added tests that prove my fix is effective or that my feature works - [x] New and existing tests pass locally with my changes - [x] Any dependent changes have been merged and published in downstream modules