Switch to sentry-go when building the reports

[yuzefovich]

Previously, we were using getsentry/raven-go to populate the reports for Sentry. However, that tool has become obsolete. This commit switches to using getsentry/sentry-go.

There are some differences in the API, and I made the following changes:

• now there can be multiple "exceptions" specified in the sentry event (previously, only one was allowed).
• "message" field will now be populated with the "head message" (a short description of the first error)
• "long message" will be included in Extra.

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This change is 

[claassistantio]

All committers have signed the CLA.

[knz]

Thank you!

For clarity, can you copy-paste a screenshot of a sentry report generated with the new code?

cc @tooolbox - I wasn't expected we'd invest in this so soon, but here you are.

[yuzefovich]

I ran the test with DSN specified as cockroachdb project, and here is what I got:

(The link to the event)

[knz]

Thank you this looks good overall. However I'd like to see how this impacts the reporting of SQL errors. I would recommend to operate as follows:

1. make sure your new code is in your $GOPATH
2. take your cockroachdb work dir and rm -rf vendor/github.com/cockroachdb/errors
3. build binary
4. make it report a SQL error (e.g. crdb_internal.force_error('XX000', 'woops')
5. see how the sentry report looks like.

Is the SQL statement included? Is it clear from the sentry message that the error was generated with force_error?

If yes then this is good to go.

[yuzefovich]

Thanks for the pointers!

I made some modifications to cockroach to use sentry-go as well, and here is the report

(and the link)

I think it looks good, right?

[knz]

Oh yeah that looks awesome. LGTM!

[knz]

After you merge this we need to bump the version because this is a backward-incompatible API change. You can add a tag for v1.3.

[yuzefovich]

TFTR!

I'll push a new tag momentarily.