Add filter_shift_swaps endpoint to schedules API

[matiasb]

Example request/response

GET /api/internal/v1/schedules/SVV8E9JGLLR9T/filter_shift_swaps/?date=2023-07-22&days=9

{
	"shift_swaps": [
		{
			"id": "SSR1QJ93UNCUPC4",
			"created_at": "2023-07-27T12:55:32.188232Z",
			"updated_at": "2023-07-28T13:28:08.027124Z",
			"status": "taken",
			"schedule": "SVV8E9JGLLR9T",
			"swap_start": "2023-07-24T21:00:00.000000Z",
			"swap_end": "2023-08-04T03:00:00.000000Z",
			"description": null,
			"beneficiary": "UWJWIN8MQ1GYL",
			"benefactor": "UVSKHRA4YU328"
		}
	]
}