Create intermediate user for channels

[coltoneshaw]

Summary

We sort channels by membership here, which looks at the membership from the slack channel and we append that to the private channels.

Then inside of the TransformChannels function we add the P type ONLY if it has > 8 valid members, here. Which in my case, not all of these channels do have valid members so that check then fails.

Then to complicate the issue, the user is created at the very end as deleted user because they own a post. So, we have these users that own posts in channels, but they're not channel members and contain no membership except town-square.

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The PR here might not have a perfect solution. However, I can confirm it resolves the problem within the import and no more channels are imported as type G, and all users (even invalid users) are now properly added to the channel membership.

[coltoneshaw]

I've broken the TestTransformPublicChannelsWithAnInvalidMember test. So, the question here I guess is, what is the expected answer?

In my mind, we need to change and build membership properly for invalid members for the reasons listed above

[coltoneshaw]

@mickmister - How do you think we should handle TestTransformPublicChannelsWithAnInvalidMember now?

[mickmister]

@coltoneshaw Is it the case that a previously "invalid" member is now "valid"? I suppose the test cases in that test function need to be adapted to take into account any new assumptions about data validity. Maybe some test cases need to be removed