All run variables remain encoded as strings in the API but will now be expressed as an HCL value to be evaluated correctly by the remote terraform. Previously, only strings were supported.

Examples:
string: `"quoted literal"` (strings must be quoted)
map:  `{ foo = "bar" }`
list: `["foo", "bar"]`
bool: `true`
null: `null`
number: `0.0001`

This requires the API to anticipate that all run variables will be HCL values