DDM: protocol handlers for tokens and declaration-items

[roperzh]

• Add logic to our nano callback functions to switch based on the mdm.DeclarativeManagement.Endpoint attribute you get here:

fleet/server/service/apple_mdm.go

Lines 2357 to 2359 in 03d1493

	func (svc *MDMAppleCheckinAndCommandService) DeclarativeManagement(*mdm.Request, *mdm.DeclarativeManagement) ([]byte, error) {
	return nil, nil
	}

• For the tokens endpoint, grab the ID of the host's team, and retrieve the the hash of the declarations for that team from team_declaration_checksum_view. Respond with a TokensResponse

{
    "DeclarationsToken": "team-hash-here",
    "Timestamp": "team-hash-timestamp-here"
}

• For the declaration-items, grab the host's team, and build a DeclarationItemsResponse based on the entries in mdm_apple_declarations, include both configurations and activations

[georgekarrv]

Hey team! Please add your planning poker estimate with Zenhub @dantecatalfamo @ghernandez345 @gillespi314 @jahzielv @mna @roperzh

[fleet-release]

Tokens and declarations,
Secure teams with affirmations,
Fleet's device relations.

In the glass city's glow,
Data flows in streams below,
Fleet's logic makes it so.

Device paths, now clear,
Through cloud's security sphere,
Fleet's promise is near.