Allow errors to be returned by webhook handler (beam-community#712)

* Allow webhook event handler to return an error state

* Update webhook plug tests with :error events

fix(deprecation): :crypto.hmac -> :crypto.mac, Bitwise.^^^ -> Bitwise…

….bxor (beam-community#669)

Merge pull request beam-community#590 from code-corps/sn/2.8

Release 2.8.0

CHANGELOG 2.7.1 (beam-community#557)

CHANGELOG 2.7 (beam-community#547)

2.6.0

Bump to 2.4 in mix

Merge pull request beam-community#494 from code-corps/release-2.2.3

Release 2.2.3

Merge pull request beam-community#442 from code-corps/release-2.2.2

Release 2.2.2