Custom Authorizer support

Adds custom authorizer support and a sample showing how to connect using a custom authorizer. Also adds support for the ClientToken field in Shadows and documentation adjustments.

What's Changed

• Fix it so CI runs on branches with '/' in name by @graebm in #236
• Added ClientToken to ShadowDeltaUpdated by @TwistedTwigleg in #241
• Autodocs by @graebm in #242
• Added custom authorizer sample by @TwistedTwigleg in #246

Full Changelog: v1.8.1...v1.8.2