[ENHANCEMENT] Deprecate failover / failback mode in 8.6 and complete removal in 8.7

[Langleu]

Describe the use case:

related to Epic: https://github.com/camunda/product-hub/issues/2173

Zeebe introduced in 8.6 a simplification of the failover and failback process. Resulting in a quicker, better, less error prone procedure in 8.6.
This results in failover and failback behaviour of the Helm chart to be obsolete. Therefore, we should remove those options global.multiregion.installationType as we should actively promote the easier new procedure.

For 8.6 the idea was to deprecate it and for 8.7 to fully remove it, giving customers a short period to get accustomed to the new procedure while still providing the old procedure during the deprecation period.

The docs were already updated as part of https://github.com/camunda/team-infrastructure-experience/issues/325 and will be visible with the next docs update.

Reason for deprecating and removing:

• Only promote simplified and less error-prone procedure
• longterm, less custom stuff to maintain

Describe the enhancement/feature:

• global.multiregion.installationType option with related failover / failback code is deprecated in 8.6
• global.multiregion.installationType option with related failover / failback code is removed in 8.7

Desired outcome and acceptance tests:

• 8.6 the value / flags are deprecated
  • implementation details and up to you on what's possible
• 8.7 the value / flags are removed

[Langleu]

@aabouzaid is this something Distribution could do for the 8.6 release and later for 8.7?

Not sure what Helm gives as possibility but as said, worst case a statement in the release notes of the Helm chart would be sufficient before finally removed in 8.7.

[aabouzaid]

@Langleu As Helm doesn't support warning messages but only fail messages, we will add it to the NOTES.txt and official docs.

[jessesimpson36]

The notes / docs are both merged. Lets create a follow-up ticket for 8.7 to make sure this option gets removed from the default values.yaml and templates. Then this ticket may be closed

[jessesimpson36]

Follow up ticket to be completed by 8.7
#2380

[jessesimpson36]

Closing this epic since deprecation work is done, and we have the new github issue #2380 which will take care of actually removing this.

[Langleu]

Thanks @jessesimpson36 🚀