BO28 - Create a DAL function to update a sponsor's logo image

[gregoriopalama]

Add a DAL function in the Sponsorship API.
The function will accept the sponsorshipID and the sponsorID.

The image should be accepted as parameter. The image will be uploaded in Firebase Storage and the public link will be used to update sponsor's document in Firestore. If a logo image is already set, it should be deleted from Firebase Storage.

The response will be an error if something goes wrong. Otherwise, the function will provide the updated sponsor object in the response's body, including the ID of the document in the DB.

Depends on #186