[mvitz]

This allows to override the ecs.version which is present in every log event and currently is set to a fixed version of 1.2.0 which is pretty old.

To preserve backwards compatibility I left the old method within EcsJsonSerializer although it is no longer called from within the library itself.

Fixes #289

[jackshirazi]

Thanks, please add test coverage for custom values, escaping, and preservation of the default behavior. Each new configuration path should ideally test both the default 1.2.0 and a custom ecs.version.

[mvitz]

@jackshirazi thanks for the review and your suggestions.

When developing the code that was submitted within this PR I already thought about testing it with the specific logging adapters, but I didn't find a good way without duplicating the test methods.

Adding a shared test into the AbstractEcsLoggingTest works for the unit tests, but I have no idea how to make this working with the integration tests, that extend from the abstract test class, too.

And for some logging frameworks, like log4j version 1, changing a base property is very difficult because it only loads from log4j.xml and we would need to versions of that configuration file.

Is there any preferred way or solution that you had in your mind?