Apply for a project

[MuhannedNoman]

Is your feature request related to a problem? Please describe.
N/A

Describe how the solution should behave
If the user is not the person who posted the project and has not already applied. They can click on the apply button and be added to the project applicant.
Don't fetch the project data again, rather mutate the state of the project and add the user locally.
Endpoint

Screenshots of the design/if any
N/A

Additional context
N/A