Add 'metrics' flag to specify available metrics

[Amerousful]

New flag to control list of available metrics due to reduce metric data size

--influxdb.metrics='mean,max'

[Amerousful]

@soulgalore Hey!) This is a PR about we discussed several days ago.
I'm not sure that the solution is okay, and maybe there's a better way to do it...

[soulgalore]

Looks good. I have two suggestions:

1. What about another name? Metrics to me sounds like a metric like first paint or something else.
2. Can you add a test case is https://github.com/sitespeedio/plugin-influxdb/blob/main/.github/workflows/linux.yml where the new option is used? That makes me comfortable that it will work over time :)

[Amerousful]

1. Totally agree with you about namings. I'll rework it.
2. Sure.

[Amerousful]

@soulgalore

1. Changed to --influxdb.functions='mean,max'
2. Add a test
3. Fix the case when, e.g. p50 isn't included in passed functions and it writes as value

if (!availableFunctions.includes(end) && !functions.includes(end))

[Amerousful]

Sorry, I have a concern about Linux. Should I add just another step with the filter by functions? And then it will be check manually in InfluxDB? I'm just worried that the previous step with all functions will mislead the check results.

[soulgalore]

I didn't fully understand the concern about Linux? One thing you could do is in the "open" function https://github.com/sitespeedio/plugin-influxdb/blob/main/lib/index.js#L20 (that is called on startup) you could verify the input of influxdb.functions and if something is broken or wrong log or throw an error before the tests start?

[Amerousful]

Copy that, I'll get it done

[Amerousful]

@soulgalore Let's run the workflow)

[soulgalore]

Thank you @Amerousful , I'll release this first thing tomorrow.

[Amerousful]

@soulgalore Thank you too) Deal.