As a volunteer I want to be able to apply for an available program

Once on the programs page, volunteers should be able to click on a non-greyed out program to apply for it (by clicking an 'apply' button in the program's card). This should open a dialog providing more information on the program, and another confirmation of this decision and the user's email should be added to a table of applicants.

**Tasks**

Frontend
- [ ] Application dialog
- For each program card created in #5, when users click on 'apply', opens a modal that shows the full description of the program as well as a confirmation button
- Clicking the confirmation button make a request to the backend and notifies the user that they have applied for the program

Backend
- [ ] Application endpoint
- POST request, given a program id, add the user as an applicant to the program