User signup request feature for non-admins

[Vedant1202]

Description

This update enables non-admins to request admins for creating new users. The admin notification menu is updated to contain both type of requests (user signup and slide deletion).

The changes are:

• Non-admins can now request for user signup.
• Admins can accept or decline the user signup requests.
• Admin notification menu has divided tabs. One for slide deletion requests and another for user signup requests (this can be viewed in the screencasts below).

**(Edit)

• Change alerts to popups on function success.
• Moved showSuccessPopup to util.js for reusability.

Motivation and Context

This will enable a non-admin to be able to request to create users, thus enhancing the flexibility of user signup process, as the signup process gets distributed within various types of users.

• It does not fix an issue as such but extends Enhanced User Signup Process #254.

How Has This Been Tested?

This feature has been tested in an environment with enabled security protocols.

• Tested on Ubuntu 18.04, Firefox browser.
• These changes do not affect other features.

Screenshots (if appropriate):

1. Non-admin creates a user signup request
   

2. Admins can either decline or accept the request.
   

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation. (@birm does it, please help?)
• I have updated the documentation accordingly.

[Vedant1202]

Yeah done, thanks.

[birm]

Ah, it looks like we've made a conflict for you... Do you mind having a look?

[Vedant1202]

Yup, done

[Vedant1202]

Changed success alerts to popup messages and moved popup function to util.js for reusability across pages

[Vedant1202]

@birm I'm done with the changes, you can review them.

[birm]

What combinations of disable sec and allow public did you test?

[Vedant1202]

@birm umm, sorry I missed the earlier comment. I tested disable security as false and true with keeping allow public as false. Please tell me if you are facing any issue over there.

Also, thanks for the suggestions, I've made the changes.

[birm]

Sorry about the confusion I've introduced with my last review.