Set default visual filter value within a M Connector

When developing a power query web connector for direct query, one needs to override triggers from the Table.View function. Specifically there is one trigger GetRows that is used to determine the values present in a filter.

The data source that we are building the connector for has the ability to select default value for filter values, for example the user can define "cast" in the above example to be the default selection. In this case, "cast" selection would be automatically applied when a filter is asked in the original data source. There has been customer asks for our connector to mimic this behaviour within Power BI, such that when a filter is added there is someway to set a default selected value within the connector such that it would selected in the filter "cast" is set as the default value.

After inquiring the internal Power BI team, they said that the connector has no way to interact with the UI in this way. If this could be made possible, it would be useful to our customers. One possible way of achieving this is to have to a "Default Value" in the metadata table that GetRows should return.