Add ability to send metrics via sentry-cli

[AbhiPrasad]

Using sentry-cli is a nice way to send metrics in bash scripts and similar.

We already have support for sending events, so this seems like a nice fit.

Ideal API:

sentry-cli send-metric gauge -n cpu_usage -v 34 -t os:MacOS -u percent

send-metric: Command to send metric. Requires argument of increment, distribution, set, or gauge (matches with our sdk public API).

Options:
-n: Name of metric (required)
-v: Metric value (required)
-u: unit (optional)
-t: tag (optional, can provide multiple)

maybe we can also somehow capture code location?

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Since these needs have evolved over the last couple of weeks, please also make sure to implement:

• tag normalization and
• rate limiting

The most recent state of current Metrics features can be found in [this doc], please check it once you plan to start the implementation of this issue, to see if there is anything else that needs to be implemented. (https://docs.google.com/spreadsheets/d/14cjYBAWI6RkDilqXYAsLYa89wIWdQJq350fjwqT1uyI/edit#gid=0)

[szokeasaurusrex]

@jan-auer Is metrics rate limiting going to be relevant for the CLI, given that each send-metrics call will originate from a separate CLI call with the proposed API? If so, I think we will need to implement this change by somehow saving the backoff information in a temp file

[elramen]

After discussing with @szokeasaurusrex, code location will not be implemented (at least not for the initial iteration).

[github-actions]

This issue has gone three weeks without activity. In another week, I will close it.

But! If you comment or otherwise update it, I will reset the clock, and if you label it Status: Backlog or Status: In Progress, I will leave it alone ... forever!

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"A weed is but an unloved flower." ― Ella Wheeler Wilcox 🥀

[AbhiPrasad]

Nice work @elramen! Looking forward to this 😄