Schedule every n days

[aws404]

This PR add the ability to schedule a run every n days.

Example Use Case

I have a system with 16 irrigation 'zones' which I split up into 3 sequences (2 zones in each), which I want to run sequentially one day after the other (ie. Day 1 = Sequence A, ... , Day 3 = Sequence C, Day 5 = Sequence A, ect.).
As the three sequences do not fit into the seven days of the week, I am unable to do this currently (as far as I can see).
This can now be achieved using the following configuration which features:

• The same number in the every_n_days option
• Incremented start_n_days to stagger the alternation

    - name: 'Sequenced Controller'
      zones:
        - name: Station 1
        - name: Station 2
        - name: Station 3
        - name: Station 4
        - name: Station 5
        - name: Station 6
      sequences:
      - name: "Program A"
        schedules:
          - time: "19:15"
            day:
              every_n_days: 3
              start_n_days: 2022-01-01 # Starting date
        zones:
        - zone_id: 1
          duration: "00:10"
        - zone_id: 2
          duration: "00:10"
      - name: "Program B"
        schedules:
          - time: "19:15"
            day:
              every_n_days: 3
              start_n_days: 2022-01-02 # Starting date + 1
        zones:
        - zone_id: 3
          duration: "00:10"
        - zone_id: 4
          duration: "00:10"
      - name: "Program C"
        schedules:
          - time: "19:15"
            day:
              every_n_days: 3
              start_n_days: 2022-01-03 # Starting date + 2
        zones:
        - zone_id: 5
          duration: "00:10"
        - zone_id: 6
          duration: "00:10"

FEEDBACK WANTED

• Is this something you would consider?
• Is inside the day option the best place for these options?
• Are these the best choices for the option names?
  • every_n_days to alternate_n_days?
  • start_n_days to alternation_start?

[rgc99]

I like the idea. Inside the day parameter probably makes the most sense. Option names are fine. Coding looks good.

The only thing that needs to be done is a test unit. Rather than add the setup to configuration.yaml create a new file in tests/configs like test_every_n_days.yaml - use test_model.yaml as an example. In the tests directory, copy test_model.py to test_every_n_days.py and adjust to suit your needs. Documentation is in the tests directory. Probably create a config that has a sequence run every 2 days, another 3 days and even another on 4 days for good measure.

The test needs to pass along with all the existing tests. If this is too much to handle I can setup the test unit.