Merge branch 'staging' into 'project-page-revisi'

# Conflicts:
#   src/main/java/com/id/ui/cs/deadliners/projectpage/controller/ForumController.java
#   src/main/java/com/id/ui/cs/deadliners/projectpage/controller/ProjectPageController.java
#   src/main/java/com/id/ui/cs/deadliners/projectpage/model/dto/ForumRequest.java
#   src/main/java/com/id/ui/cs/deadliners/projectpage/service/ForumService.java
#   src/main/java/com/id/ui/cs/deadliners/projectpage/service/ForumServiceImpl.java
#   src/main/resources/templates/project-page/detail_forum.html
#   src/main/resources/templates/project-page/project_page.html
#   src/test/java/com/id/ui/cs/deadliners/projectpage/model/ForumTest.java
#   src/test/java/com/id/ui/cs/deadliners/projectpage/service/ForumServiceTest.java