Coverage

added result and error handling tests for APIs behind paywalls (those which do not get tested along with the others)

added converter.active test + reduced provider setup complexity by removing keyNeeded (if %KEY% is present in the template url string, the stored key will be inserted)

Error handling

removed config from Converter to avoid confusion; caching will be implemented in a separate type of converter. Added provider getters

Conversion

Providers

Request handlers