Verify if MFA assignments changed before emitting an event

[j-chmielewski]

In modify_network handler, before emitting a LocationMfaFlowsAssigned event, check if the flows really changed:

    // TODO: also check new-old assignments equality before emitting
    if update_mfa_assignments {
        appstate.emit_event(ApiEvent {
            context: context.clone(),
            event: Box::new(ApiEventType::LocationMfaFlowsAssigned {
                location_id: network.id,
                location_name: network.name.clone(),
                assignments: LocationMfaFlowAssignment::snapshot(&mfa_assignments),
            }),
        })?;
    }