2116 improve resilience of posthog integration

[collinpreston]

What are the relevant tickets?

#2116

Description (What does it do?)

1. Adds POSTHOG_FEATURE_FLAG_REQUEST_TIMEOUT_MS as an environment variable. Default is 3000 milliseconds.
2. Adds POSTHOG_MAX_RETRIES as an environment variable. Default is 3.
3. Defines feature_flags_request_timeout_seconds as an option when calling PostHog (https://posthog.com/docs/feature-flags/adding-feature-flag-code#request-timeout).
4. Rename IN_TEST_SUITE to POSTHOG_ENABLED.

Testing

1. PostHog functionality should not be impacted when running MITx Online locally. POSTHOG_ENABLED should be set to True locally.
2. If you define POSTHOG_FEATURE_FLAG_REQUEST_TIMEOUT_MS=1 in your .env file and restart MITx Online. When you load the homepage you should not see any features that require the feature flags to be active.
3. If you define POSTHOG_FEATURE_FLAG_REQUEST_TIMEOUT_MS=3000 in your .env file and restart MITx Online. When you load the homepage you should see features that require the feature flags to be active.

[jkachel]

I was looking through this and it seems pretty close to the implementation that's in Open. Rather than squaring these two implementations up, should they be merged and put instead into ol-django's common app? That way MITx Online and Open will have consistent implementations (and MITx Online would gain a local feature flag cache). Thoughts?

[collinpreston]

I was looking through this and it seems pretty close to the implementation that's in Open. Rather than squaring these two implementations up, should they be merged and put instead into ol-django's common app? That way MITx Online and Open will have consistent implementations (and MITx Online would gain a local feature flag cache). Thoughts?

Sure that sounds good.

[collinpreston]

Closing in favor of mitodl/ol-django#152 which will be followed up with an accompanying MITx Online PR to incorporate the ol-django PR.