[Discussion] - Breaking change resulting from data type changes of mapped attributes #13861

In some scenarios we might have to make subsequent updates to existing integrations where the update would involve changing the data type of an existing mapped attribute.

This could be because of reasons such as :-

1. Existing attribute was initially assigned a wrong type.
2. Updates in the original data source/ api has changed the original data type due to internal reasons.
3. Performance reasons (this would be very rare), where indexing the data with it's original data type is becoming expensive for the end-user. etc ...

In such cases, an update made to change the data type would be considered a breaking as it would create conflicts in kibana search queries / dashboards (if they were being used). Till now we have generally followed the philosophy of incrementing the major version of integrations when it comes to breaking changes. However in some cases such breaking changes have been assessed to have minimal impact mainly due to -

1. The attribute was very recently introduced in the integration and has not seen much use.
2. The attribute is not being used in Kibana dashboards at all.
3. The attribute might not have been even indexed in the first place due to data type mis-match.

Such a case was recently occurred in this PR, and in the discussion here it was clarified that even if a field is not explicitly indexed (because of a data type mismatch), it is still explicitly mapped and that would be enough for conflicts to occur when the backing index for the data stream gets created, more details in the discussion.

After discussions across the team it was how ever assessed that the impact of this change would be minimal, and the conflicts would self correct with an index rollover and passage of time, hence it was decided to mark this particular PR as a bugfix and not a breaking-change. It was also kind of decided that we would analyse such cases moving forward on a case by case basis and decide if they are significant to be a breaking-change or a bugfix.

Recently another such PR has come into play, where there is a data type change leading to a breaking-change. However we have only done an increment for the "minor" version here (which is generally reserved for enhancements) and marked it as a breaking-change.

The issue is that there seems to be a bit of confusion on how to handle the version increments and the type of change it should be marked as due to the case-case policy we are going by at the moment.

Issues resulting from a case-by-case approach:

1. Lack of clarity regarding version increments.
2. Incrementing major versions often for such small but impactful changes can cause disruption in the community and with end users in general.
3. Often hard to assess the impact of these changes for end users without team wide consultation, since the data volume and persistence can vary from user to user.
4. Such changes can often result in SDH's if support is not made aware and such a change is done without a major version increment.
5. Such a strategy can lead to PR history confusion if each of the PR's don't justify in detail why a certain version increment was made and why it was tagged with a breaking-change/enhancement/bugfix.

Questions:

1. Should we keep a generic template for such changes if we are to adopt such a case-by-case strategy ?
2. Should we adopt a single standard for all such changes in future for end-user clarity, as this would standardize all future PR's making such a change?
3. What kind of community awareness / support awareness should we provide when such changes are published ?
4. For very popular and widely used integrations should we always do an impact analysis before making such changes or avoid such changes in the first place and take a workaround approach by introducing a separate variable to account for the fixed data type ?

cc: @elastic/security-service-integrations @elastic/sit-crest-contractors @andrewkroh @narph