Add Attachment support

[bruno-garcia]

The native SDKs (sentry-android, sentry-cocoa) added support to Attachments.

The spec is in the develop docs.

Thumbs up if this is the feature you've been waiting for.

[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!

---

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

[renchap]

In addition to this, it would be awesome to be able to run a callback when an error happen and generate attachments from this callback.

I have multiple states in the app (Redux, async storage…) and I would like to dump them in attachments when an issue occurs in the app to be able to understand the error if it comes from a bad state.
Currently I could add them to the event, but it can quickly go over the 200kb limit.

[marandaneto]

This is blocked by getsentry/sentry-javascript#4240

The RN SDK uses the JS SDK for building an event and the current version does not support the Envelope feature which is required for sending attachments.

To make it work we'd need to override many of the JS behavior and later replace them once the Envelope feature is landed on the linked PR natively on the JS SDK.

The best is to postpone and implement once #4240 is done, also considering attaching attachments to hard crashes on the Native layer.

Points to consider:

• Use the envelope feature from feat(core): Exclude Dev Server and Sentry Dsn request from Breadcrumbs #4240
• Attach attachments on hard crashes, that requires changes on Sentry-Android, Sentry-Native, and Sentry-Cocoa since we don't sync down the attachments to the Native layers (e.g. KSCrash and Sentry-Native)
• We could technically support an array of bytes and file paths since RN does not support files natively, people most of the time use 3rd party plugins to do so.