* adds CLI commands for add/set/removing worker tags, and respective tests
* adds StringSliceMapVar Flag to convert a string from the CLI to a map[string][]string value
This allows a check function to be set to determine whether it is
allowed to be set. This also ensures that if null is allowed it is
either the only value or not set.
For a flag type used for attributes/secrets, values have always been
able to be used with env:// or file:// format, but the error check to
see whether the value was successfully parsed was doing a simple string
equality rather than `errors.Is`. As a result a value containing a colon
would trip up this check and cause an error, rather than allowing it to
be used as a bare value.
I've pulled over files as-is for the most part so this also pulls over
some common attribute/secret flags but it's not worth dealing with the
merge later...
Haotian
Jeff Mitchell