Milestone | Delete

### User Story
As a user, I need to be able to remove milestone from the milestone's collection. When I identify a milestone that needs to be removed, I want to initiate the deletion process. If the project I intend to delete is not found, the system should provide a message indicating that the project is not available for deletion.

### Task
- [ ] Implement Data Access Object (DAO) Layer.
- [ ] Implement Service Layer.
- [ ] Create JUnit Test Cases.
- [ ] Ensure that the tests cases are passing.
- [ ] Write clear and concise comments in the code to explain complex logic.
### DAO
- [ ] deletemilestone()
- [ ] Service
- [ ] deletemilestone()
### Junit Test
- [ ] testValidDeletemilestone()
- [ ] testInvalidDeletemilestone()
### Estimation
3 hours

### Flow Chart:
``` mermaid
graph TD
A[[Start]] --> B(User Initiates Delete Milestone)
B --> C[(Search Milestone to Delete)]
C --> |Milestone Not Found| D{{Service Exception}}
D --> |Fail| E([Failed to Delete Milestone])
C --> |Milestone Found| G([Confirm Deletion])
G --> |Delete Milestone Record| F([Milestone Deleted Successfully])
E --> |Returns False|I[[End]]
F --> |Returns True|I

style F fill:#dfd,stroke:#333
style E fill:#fdd,stroke:#333

```