Hxl-proxy

- remove controller support for adding or editing saved recipes
- request code stops running after a configurable timeout (default: 30 seconds)
- remove skip-verify-ssl option (SSL certificates for remote data must always be valid)
- add support for structured logs (e.g. JSON)
- add support for Visual Studio
- remove all frozen version requirements (except urllib3 for requests), so that we'll pull the latest packages on deployment
- get rid of warnings during user testing

- interim release to upgrade libhxl to 4.27.3 (decreased logging levels)

- interim release to address performance issues
- change Docker config to use threads with nginx
- make root logging level configurable via ROOT_LOGGING_LEVEL config property (and default to INFO instead of DEBUG)

- add REMOTE_ACCESS_LOGGING_LEVEL to filter "hxl.REMOTE_ACCESS" separately to show remote file access (currently,
all messages will be at the INFO level)
- show the same error message for a non-existant remote data file, or for a URL that contains HTML markup; prevents
bad actors from using the HXL Proxy to ping HTML websites
- don't trap 404 and HTML markup exceptions in the /data/edit endpoint
- forbid HTML markup or URLs in saved-recipe titles, descriptions, and stubs to cut down on spam attempts

- downgrade to mysql-connector-python==8.0.29 to avoid bug in 8.0.30

- add MAX_REQUEST_TIMEOUT configuration option, to place a cap on the maximum allowable timeout for reading external datasets
- add LOGGING_LEVEL configuration option (defaults to "ERROR")
- log warnings for exceptions caught and returned as web pages with 400/500-series status codes