Avoid generating uncompilable response body in Spring's API template (2023)

[smasset]

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Description of the PR

Creating new PR as suggested in #8691

If definitions start to get complicated, example response bodies can exceed Java compiler's limit for constant strings.

This PR addresses this issue by introducing and using two new lambdas to remove any unnecessary whitespace and (if still needed) to split the constant string into smaller compilable parts using a StringBuilder to merge them back again.

Fixes #9055.

[diyfr]

@smasset I am not a maintainer so I cannot validate any PR.
See with https://github.com/orgs/swagger-api/people

@frantuma @HugoMario