Employee Module | Employee Leave Details

- [x] Applying and approval of leaves

Only managers can approve a leave. Leave application table will have employee
applying for a leave and status is applied. Manager once approve status will change as approved

- [x] Tracking of leaves

Each leave type will have maximum leaves. CL will have 10 days,
sick leaves 5 days per year. For each employee it should show how many leaves are pending.

**employee_leave_details**
| Column | Data Type | Constraints |
|----------------|--------------|-----------------------------------------------|
| id | int | not null, auto_increment, primary key |
| employee_id | int | not null, foreign key (employee(id)) |
| leave_type | varchar(2) | not null, foreign key (leave_types(name)) |
| start_date | date | not null |
| end_date | date | not null |
| no_of_days | double | not null |
| leave_reason | varchar(100) | not null |
| status | varchar(20) | not null |
| applied_on | timestamp | default current_timestamp |
| manager_id | int | foreign key (employee(id)) |
| comments | varchar(200) | |