[Backend] Add student name based search for attendance api

[dreamingblackcat]

Right now, the search we have right now in Attendance page is a placeholder implementation only searching in the current page.

What we would like to get is a search that works with the backend and gives all matching results.

For that, we need to support keyword search in /attendances endpoint.

I am using keyword param for search keyword. So, the api should now support keyword param in addition to existing grade and year parameters.

Also please make sure that we can give those filters in any combination. Just only one or just two or all three for example.

(Refer #176 for frontend portion of this)

[khinezarthwe]

Current get all attendance endpoint

• add keyword search endpoint for attendance ->/api/v1/attendances?grade=XXX&year=XXX&keyword=name
• keyword should search for related student name
  Please refer to (https://github.com/thingaha/thingaha-web/blob/master/backend/docs/donation.md#get-all-donations)