Provide EF.Functions translations for JSON functions

[roji]

For users using JSON without a strongly-typed schema, mapping the column as a string is the only option at the moment. We should provide translations for JSON_VALUE/JSON_QUERY for SQL Server and json_extract for SQLite.

[joelmandell]

If this is up for grabs I might look into it @roji

[roji]

@joelmandell sure, go ahead - the "good first issue" label is a good indication that it's a relatively accessible issue that external contributors can work on (but always good to check).

[joelmandell]

Hi @roji,
I tried to add an IMethodCallTranslator for JSON_VALUE for the SqlServer provider. But the Translate() method is never called. I am having a hard time finding out why it is not being picked up. Do you have anything that can point me to in the correct direction?