chore: update LICENSE to AGPL 3.0

[jalling97]

Description

• Updates the LICENSE.md to AGPL 3.0

• Adds LICENSING.md

• Replaces Apache 2.0 SPDX headers with AGPL 3.0 headers

• Adds missing SPDX headers

• Updates CODEOWNERS

• Bug fix (non-breaking change which fixes an issue)

• New feature (non-breaking change which adds functionality)

• Other (security config, docs update, etc)

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

[catsby]

cc @austenbryan I think is good-to-go

[jeff-mccoy]

This is missing some of the changes used in uds-common such as CODEOWNERS update, SPDX headers, and LICENSING file, see defenseunicorns/uds-common#286 for an example (and lint task)

[mjnagel]

We'll need to go through all the existing files with license headers as well and update them, example: https://github.com/defenseunicorns/uds-cli/blob/main/src/pkg/engine/k8s/common.go#L1-L2. addlicense doesn't touch any existing headers in files so you may have to find and replace/nuke all the old ones first.

[catsby]

@jeff-mccoy @austenbryan I believe this is updated and ready. Big thank you to @jalling97 for 99% of the work here. I added a github workflow to validate license headers going forward, the rest was their work. Thanks!

[austenbryan]

Approving license fill changes

[daveworth]

approving CODEOWNERS changes but nothing else

[UncleGedd]

YOLO