feat: Add decision starter API for email flows (#4533)

Co-authored-by: hyperswitch-bot[bot] <148525504+hyperswitch-bot[bot]@users.noreply.github.com>
Files to modify:


**user.rs**
  Modify existing code

**user.rs**
  Modify existing code

**user.rs**
  Modify existing code

**app.rs**
  Modify existing code

**lock_utils.rs**
  Modify existing code

**user.rs**
  Modify existing code

**types.rs**
  Add:
    - function: pub::get_flow

**decision_manager.rs**
  Add:
    - function: pub::get_token

**types.rs**
  Add:
    - function: pub::get_flow