Provide the ability to supply additional headers and additional URI parts for Web Api Connector in Data Flow Gen 2

Currently, Data Flow Gen 2 Web Api Connector works differently than Power BI Desktop and Pipelines in power bi. In both the other platforms, you can choose anonymous and provide extra information, such as headers and additional URI parts when trying to set up a data source. Currently, when choosing anonymous in data flow gen 2 and selecting Web API, there is no such opportunity, and therefore apis that rely on static token headers fail. Litmos is an example of one of these apis, but there are a lot out there that rely on header tokens for authentication.