Backend DELETE endpoint for room slot

[pconrad]

User Story

• As a developer, logged in with a user that has admin access, accessing the backend through swagger-ui/index.html
• I can access a DELETE endpoint that will allow me to delete room slots by id
• So that I have the backend features needed to implement deleting from the front endf

Sample Code

• A DELETE endpoint from Courses: https://github.com/ucsb-cs156-s21/proj-ucsb-cs-las/blob/114605ab1a57568ff9b15f991e0fd4c7c36585ea/src/main/java/edu/ucsb/ucsbcslas/controllers/CourseController.java#L114-L125

Sample Tests

• tests for a DELETE endpoint for courses: https://github.com/ucsb-cs156-s21/proj-ucsb-cs-las/blob/114605ab1a57568ff9b15f991e0fd4c7c36585ea/src/test/java/edu/ucsb/ucsbcslas/controllers/CourseControllerTests.java#L271-L307

[pconrad]

Estimated at 10 points

[pconrad]

Already done in a previous PR:

• PR: #269
• code: https://github.com/ucsb-cs156-s21/proj-ucsb-cs-las/blob/114605ab1a57568ff9b15f991e0fd4c7c36585ea/src/main/java/edu/ucsb/ucsbcslas/controllers/RoomSlotController.java#L64-L78