Decide the final form of existing copyright notices in the source code

[gotwarlost]

• Currently we have 16 lines of copyright clauses in every source file
• The opensource team at Elastic has indicated that they would like to see verbiage similar to the following

  Copyright 2023-2024 Elasticsearch B.V.
  Copyright 2024- The Crossplane Authors.

• Is the above acceptable to everyone? Should we add on to existing text or replace existing text with the above?

cc: @negz @gtback @jamietanna

[gtback]

From my perspective, the important parts are:

• The Elasticsearch B.V. copyright notice being retained in every file (of course, new files beyond our initial contribution don't need that).
• It clearly being stated that the code is under the Apache 2.0 License (if that ever changed, we would need to be consulted about relicensing Elastic's contributions).

Elastic's policy is to include the Apache 2 License header in each file, but I don't think that is strictly required here, as long as the above two goals are met, via package metadata, LICENSE (or similar) file at the root of the repo, SPDX License Headers, etc. Whatever matches the Crossplane project conventions is most likely fine. If you want an "official" response from our legal folks, I can ask them to comment on whatever you're planning to do.

[negz]

That all sounds good to me.