[FR] Stream line more with HA architecture; last_reported and availability

[erkr]

Hi

Thirst thanks for maintaining the RFLINK integration in HA. I'm using it for several years and it works great.
In the mean time HA architecture for integration entities evolved, and I believe RFLINK could be more streamlined.

My FR is to add availability awareness and last reported to RFLINK sensors.

Sensor example:

      oregonv1_004c_temp:
        sensor_type: temperature
        name: rf433 Tuinhuis Temperature

      oregonv1_004c_update_time:
        sensor_type: timestamp
        name: rf433 Tuinhuis update_time
        unit_of_measurement: 's'

This update_time sensor is created by RFLINK, but it would be more consistent to remove this extra sensor and use it for availability and last reported instead.
For availability a configurable timeout would be enough with (default 0 for no timeout to stay backwards compatibile)

Configuration would then become:

      oregonv1_004c_temp:
        sensor_type: temperature
        name: rf433 Tuinhuis Temperature
        availability: 600 #seconds

In the general RFLINK config section you could add an option to disable these extra update_time sensors (default false to stay backwards compatibile)

My 2 cents
Eric