Implemented a route for updating email address

[sachinsom93]

Description

This PR deals with :

1. This route works accordingly to user's role
   2 if user is admin, it will changes his email alongwith all the
   admin field of his users
2. and if role of user is not admin then only his email will udpated
3. Also handled all the possible errors like
   • Missing parameters
   • check for registered email id
   • checked that previous email should not be equal to new email id

Fixes #98

Type of change

• 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)
• This change requires a documentation update

How Has This Been Tested?

Manually using Postman

Test Configuration:

Also, include screenshots for the verification and reviewing purpose.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules