feature(datastore): adds in, not-in, and != query operators

[telpirion]

This PR was previously merged and then reverted.

Waiting for feature to be launched.

[telpirion]

Per @kolea2 : Be sure to add integration tests

[telpirion]

Logged #6184 to track enabling the integration tests for this feature.

[lixin9311]

Hi, thanks for releasing this feature.

Is it possible that we could change the signature of the FilterField(fieldName, operator string, value interface{}) into FilterField(fieldName, operator string, value ...interface{})?
So that we could make our code much clear if we want to use the IN query.

baseQuery.FilterField("I", "not-in", []interface{}{1, 3, 5, 7})

baseQuery.FilterField("I", "not-in", 1, 3, 5, 7)

As for equality queries, we can take the first element of the value, or panic if there is no given value.

[telpirion]

Hi @lixin9311 ! Thank you for your message.

In the future, it's probably best to log an issue in the repo to ask for a feature request. That said, I don't think that I'll accept your requested change. I think that adding a variadic value to account for array values isn't going to be useful for most customers.