Remove default replay sample rates

[mydea]

I would like to get rid of the default sample rates we have defined, because IMHO it can be confusing. Currently, we have the following default values:

replaysSessionSampleRate: 0.1, 
replaysOnErrorSampleRate: 1

While these values are good defaults, the problem with defaults is that it is "magic" - e.g. if I set this config:

Sentry.init({
 replaysOnErrorSampleRate: 1
})

it is IMHO not clear that we will still capture "regular" replays 10% of the time. The same way vice versa, with the current setup replays will by default ALWAYS be captured, meaning each and every user will have the impact of replay running, even if I configure e.g.:

Sentry.init({
 replaysSessionSampleRate: 0.1
})

due to the error sample rate being 100% by default.
We also don't have this for other rates, so I'd propose to default them to 0. And just make sure in all docs to always provide both values as defaults to copy-paste.

[mydea]

cc @bruno-garcia @billyvg @Lms24

[bruno-garcia]

Thanks for raising this. This makes sense.

Some thoughts:
1. The "Error feature" has a sample option, that without being set equals to 100% (e.g: ppl expect all errors captured by default).
2. Transaction can almost always be too much at 100%, so without defining a sample rate, the SDK is completely disabled.

Using that analogy, we could consider:
1. Keep the current 100% sample of errored sessions. Document it as such, and give advice for alternative sample rates.
~2. Set the session sample rate to 0 by default. Keep 0.1% on the docs/wizard though. ~

Since the ratio between sessions and errors isn't really 1:1 since we notice a session that has error often has more than 1 error. But even then, since quotas are not equal by default, the starting experience could be that users would run out of sessions quickly.

Another alternative is to have them both equal to 0% if unset. Basically "turned off".

I believe we should continue to document the explicit sample rates usage. And not rely on new Reply having any sampling set. Thoughts? Let's align before we agree on the route.

[bruno-garcia]

Just realized the docs actually point out the default values: https://docs.sentry.io/platforms/javascript/session-replay/configuration/
Need to be updated once/if we change this

[bruno-garcia]

This has come up on Twitter: https://twitter.com/tuncaozan/status/1616026107278417921?s=46&t=vXzl2tIH2zSYpfvrJYaKIw