* Slack: add support for blocks
* Slack: drop unused validate_certs option
* Slack: update docs to reflect thread_id can be sent with tokens other than WebAPI
* Slack: drop escaping of quotes and apostrophes
* Slack: typo
* Revert "Slack: drop escaping of quotes and apostrophes"
This reverts commit bc6120907e.
* Revert "Slack: drop unused validate_certs option"
This reverts commit a981ee6bca.
* Slack: other/minor PR feedback
* Slack: add changelog fragment
* Slack: clean-up/clarify use of recursive escaping function
* Slack: PR feedback
Co-authored-by: Lee Goolsbee <lgoolsbee@atlassian.com>