[ENHANCEMENT] Adding some support for carbon.txt in our detailed checkers and API involves us

[mrchrisadams]

Adding some support for carbon.txt in our detailed checkers and API involves a few changes:

• We need to make the extended lookup explicitly tell you when a lookup has been connected to a provider via the green domains table.
• We need to update the API to support these carbon.txt lookups, even in nocache mode. At present, a no-cache API check can delete the greendomain instance, )
• We need to update our carbon-txt preview page to allow folks to see how Via and DNS lookups are affecting which file is parsed At present, we do not surface this - we just show matching providers for each domain.