TEL-730: Add validation method variants that include soft errors.

[alexfish8]

This PR adds ValidateResult variants of some of the existing SIP Validate methods. Logically, these are the same as the current ones, except they return a ValidationResult instead of an error, where said ValidationResult is composed of an error and zero or more "soft validation errors".

Context: for certain kinds of validation failures, we'd like to log something, but swallow the error, so that the surrounding processing might still continue (we call these "soft errors"). There already exists a mechanism for logging these "soft" errors (SoftFailureReporter), but the SoftFailure reporter is global, and so it is cumbersome to pass the SoftFailure reporter request-scoped logging context (note: I had originally experimented with extending the SoftFailureReporter function signature to include a Context and adding flavors of the Validate methods that had a Context parameter, but this felt a bit error-prone).

Now, if callers want to log soft validation errors, they may do so by invoking theValidateResult variant of the Validate method and logging the soft errors of the returned value.

General notes:

• Initially, when I wrote this, I had added variants of Validate that returned an []error rather than a ValidationResult (where the error slice contained both hard and soft errors). This was simpler in some ways (avoided introducing a new type), but it became a bit annoying to continually re-check for hard errors in various contexts. This motivated me to add a new type with a simple OK() method that could allow callers to conveniently check whether or not they should continue processing or not.
• In the future, we might consider extending ValidationResult to contain a slice of hard errors. For now, I've opted to keep behavioral changes to a minimum, so that the validation logic will continue to eagerly return if a hard error is encountered.
• Added various utility methods for logging and combining ValidationResults (thanks @alexlivekit for the LogSoftErrors suggestion!).

Example of how these methods will be used

[changeset-bot]

🦋 Changeset detected

Latest commit: 5c42903

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
github.com/livekit/protocol	Minor
@livekit/protocol	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[CLAassistant]

All committers have signed the CLA.

[alexlivekit]

a few nits, but overall lgtm

[alexfish8]

a few nits, but overall lgtm

Thanks for the review!