Ignore unknown request fields

[whatyouhide]

Closes #663.

If the goal of Sentry is to never get in the way and never cause issues itself, then maybe a better strategy here is to ignore unknown request keys instead of raising. I did some testing and it turns out that Sentry itself ignores unknown keys in the request interface, so this strategy seems solid.

[sl0thentr0py]

yes in general, we want to fail gracefully in the SDK as much as possible.

Order of priorities:

• fail gracefully, never break user code (if monkeypatching - make sure they're idempotent)
• collect correct data