Upgrade FBCAPI version to v20

[itsarijitray]

This Pull request is to update API version from v18 to v20 in Facebook Conversions API.

We upgrading Facebook Marketing API upgrade to v20 as v18 is slated for deprecation by August 13, 2024.

Ticket: https://segment.atlassian.net/browse/STRATCONN-3925

A flag based rollout will be done for the integration where if the flag is enabled, the API will accept the newer canary version for the Facebook APIs.

Monitoring for the flag rollout can be done through the below datadog dashboard.

Flag on gate: https://flagon.segment.com/families/centrifuge-destinations/gates/facebook-capi-actions-canary-version

Datadog Dashboard: https://segment.datadoghq.com/dashboard/ndz-m7d-w2g/facebook-destinations?fromUser=false&refresh_mode=sliding&tpl_var_environment%5B0%5D=stage&view=spans&from_ts=1721394535441&to_ts=1721999335441&live=true

Testing

Stage Test Screenshots:

Datadog Link: https://segment.datadoghq.com/dashboard/ndz-m7d-w2g?fromUser=true&refresh_mode=sliding&tpl_var_environment%5B0%5D=stage&tpl_var_integration=facebook-app-events&view=spans&from_ts=1721388193311&to_ts=1721389093311&live=true

Include any additional information about the testing you have completed to
ensure your changes behave as expected. For a speedy review, please check
any of the tasks you completed below during your testing.

• Added unit tests for new functionality
• Tested end-to-end using the local server
• [Segmenters] Tested in the staging environment

[nick-Ag]

Hey @itsarijitray - would you mind expanding the description with some details on how you tested? ie: what routes did you hit? Did you send thru data and verify it arrived in the destination? Did you test the oauth flow (if applicable)?

[itsarijitray]

Hey @itsarijitray - would you mind expanding the description with some details on how you tested? ie: what routes did you hit? Did you send thru data and verify it arrived in the destination? Did you test the oauth flow (if applicable)?

Hey @nick-Ag, This PR is WIP. Marking it as draft.

[brennan]

Thanks, @itsarijitray, what is the plan and cadence for the rollout? Once you decide, please add the schedule to your test doc, the related Jira ticket, and please announce rollout to new tiers in Slack. 🚀