chore!: Use serde_json::Value instead of String for user-provided JSON configOverrides

[sbernauer]

Description

Feedback from stackabletech/opensearch-operator#137

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added

[dervoeti]

Thanks!

[dervoeti]

Suggested change

	- BREAKING: Use `serde_json::Value` instead of `String` for user-provided JSON configOverrides. This changed is marked as breaking, as it causes a breaking change to the CRD ([#1206]).
	- BREAKING: Use `serde_json::Value` instead of `String` for user-provided JSON configOverrides. This change is marked as breaking, as it causes a breaking change to the CRD ([#1206]).