Check whether gas readings are optional about dsmr-reader

[dennissiemensma]

Original comment by Dennis Siemensma (Bitbucket: dennissiemensma, GitHub: dennissiemensma):

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DsmrReading 's extra_device_timestamp & extra_device_delivered should be nullable.

[dennissiemensma]

This issue is required for @danielterhorst as he does not have a meter which supports gas readings.

[dennissiemensma]

@danielterhorst heb je toevallig een snapshot van je DSMR telegram?

Of mis je gewoon deze velden onderaan?

0-1:24.1.0(003)
0-1:96.1.0(xxxxxx-lang-id-van-meter-xxxxxxxxxxxxxxxxxx)
0-1:24.2.1(160229190000W)(01234.567*m3)

[dennissiemensma]

Altered database to allow nullable extra devices. Tests work fine now, after defaulting some values to None:

        if with_gas:
            data += [
                "0-1:24.1.0(003)\n",
                "0-1:96.1.0(xxxxxxxxxxxxx)\n",
                "0-1:24.2.1(151110190000W)(00845.206*m3)\n",
                "0-1:24.4.0(1)\n",
            ]

Next up are all the services expecting to have at least gas consumption tracked.

[dennissiemensma]

Refactored the tests a bit. Created separate fixtures without gas data, sub classed the tests and altered the fixtures, having them execute the same tests, with different data.

Any code depending on gas readings came forward. Although it's all just based on asumptions without a production example.

[dennissiemensma]

Added some checks to interface. Will continue later. Merged to default for now.

[dennissiemensma]

Flushing the database for checking whether the views run without data does not work for postgresql and mysql. I'll have to refactor that later, by just calling the model's .objects.all().delete() instead of call_command.

[dennissiemensma]

Fixed tests, as they failed for mysql & postgres when calling flush, which wrapped an transaction inside another transaction and failed.

[dennissiemensma]

As the gas is now optional, technically, I think I'll close this one and have #70 as followup. Which points to the actual interface and capabilities regarding gas & electricity returned.

[dennissiemensma]

./test-all.sh once again passes the tests for all backends supported.

Merged & deployed.