Needs Revision: Signup, Login, Password Recovery & Profile Editing

[1000miles]

The signup, login, password recovery and profile editing process needs a revision because at some parts the redirections, flash messages and email messages don't follow a logical concept anymore since the signup/login authentication has been moved to openstreetmap.

This ticket is a parent task to collect all the subtasks.

Example:

• [ ] On profile edit page: Flash message[success] not working properly #176
• [x] On after signup edit page: form validation not working properly #175
• [x] On after signup edit page: alert message duplicate appears when providing email address #181

[holgerd]

related: #349

[holgerd]

on hold, waiting for PR #359 to review this.