Add new DRF APIs for Alerts data

[Lorygold]

Implement 2 Django Rest Framework APIs:

AlertsAPI

Input: start and end datetime
Output: a JSON with a list of dictionaries each of which contains the timestamp, username and rule of the Alert triggered.
Example:

[
	{
	 "timestamp": "2023-06-15T14:00:00Z",
	 "username": "Lorena Goldoni",
	 "rule_name": "Impossible travel detected"
	},
	{"timestamp": "2023-06-15T14:30:00Z",
	 "username": "Lorena Goldoni",
	 "rule_name": "Login from new country"
	}
]

RiskScoreAPI

Input: start and end datetime
Output: a JSON with username as keys and the risk score as value.
Example:

{
	"Lorena Goldoni": "No risk",
	"Lory Goldoni": "High"
}