Add possiblity for users to apply for published projects

Create a second way of adding members to a project. A user can apply for a project, and the project admin can approve or deny the request.

Published flag is added, and can be set in the /admin/project/show-local-project.xhtml page.

/project/list-public-projects.xhtml exists as a stub. Should contain the short description and the projects should be clickable. A click opens another page like i.e. /project/show-public-project-detail.xhtml

On the detail page, there should be the Name, short and full description of the project (without editing). Remove ID line.

Introduce new edu.kit.scc.webreg.entity.project.ProjectMembershipType: APPLICANT which will represent Project-members that need to be approved by PI (ProjectIdentityAdminEntity)

Introduce new edu.kit.scc.webreg.entity.project.ProjectMembershipType: NOTMEMBER which will represent user that applied for the project but were rejected by Project PI

PI/ProjectAdmin needs button to approve or deny project applicants on /project/show-local-project.xhtml (perhaps besides the trashcan)

• Approve button: PI may provide a reason (not required field) to approve the project membership request.
• Deny button: PI must provide a reason (required field) to reject the project membership request.

On the user side (/project/show-public-project-detail.html?id=1249861) is visible details about the project itself, project membership status and the reason why their request was approved/denied by PI.