feat(feature-flags): v3 json payloads

[EDsCODE]

Problem

• accept JSON payloads on all flags
• feature flag filters can now parse payloads for boolean values
• feature flag filters variants can now parse payload per variant
• decide endpoint v=3 will return a new key featureFlagPayloads that returns a dictionary of matched keys to payload

Changes

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How did you test this code?

[posthog-bot]

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[neilkakkar]

You don't need to add this, since it's for the backwards compatible case. Makes it more confusing 😅 .

This is for the case where the groups key is not in filters, and there's a direct properties key instead. There's no way for the payload to be here.

We might be able to remove this completely, depending on if any old clients remain.

[EDsCODE]

There's a related failing test here. Checking again

[neilkakkar]

Last valid such flag was in Jan 2021: https://metabase.posthog.net/question#eyJkYXRhc2V0X3F1ZXJ5Ijp7ImRhdGFiYXNlIjozLCJ0eXBlIjoicXVlcnkiLCJxdWVyeSI6eyJzb3VyY2UtdGFibGUiOjQ3LCJmaWx0ZXIiOlsiYW5kIixbImlzLW51bGwiLFsiZmllbGQiLDIzODE5LG51bGxdXV0sIm9yZGVyLWJ5IjpbWyJhc2MiLFsiZmllbGQiLDM4OCxudWxsXV1dfX0sImRpc3BsYXkiOiJ0YWJsZSIsInZpc3VhbGl6YXRpb25fc2V0dGluZ3MiOnt9LCJvcmlnaW5hbF9jYXJkX2lkIjpudWxsfQ==

There does seem to be a lot of trash created too though, where filters are completely empty. Should guard against that, I'll add that in a follow up

[neilkakkar]

pending the two comments, looks good to me!

[neilkakkar]

re: failing test, the problem is you're using the old way to create flags (direct property key), with payloads, which should be impossible in the new UI, since we always use {"groups": []} now

[EDsCODE]

Yeah got it. The backwards compatible code is so hectic

[neilkakkar]

2 nits okay for followup: ebafa3f#comments