docs: standardize license headers

[kevgo]

Add license headers clarifying the copyright of source code files.

Related Issue or Design Document

https://github.com/ory-corp/general/issues/602

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact security@ory.sh) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

[codecov]

Codecov Report

Merging #1024 (2b187f7) into master (f810a0b) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1024      +/-   ##
==========================================
+ Coverage   78.66%   78.70%   +0.04%     
==========================================
  Files          83       83              
  Lines        3866     3869       +3     
==========================================
+ Hits         3041     3045       +4     
+ Misses        555      554       -1     
  Partials      270      270              

Impacted Files	Coverage Δ
api/credential.go	75.60% <ø> (ø)
api/decision.go	95.55% <ø> (ø)
api/health.go	0.00% <ø> (ø)
api/rule.go	52.17% <ø> (ø)
cmd/credentials.go	100.00% <ø> (ø)
cmd/credentials_generate.go	100.00% <ø> (ø)
cmd/health.go	50.00% <ø> (ø)
cmd/health_alive.go	77.77% <ø> (ø)
cmd/health_ready.go	77.77% <ø> (ø)
cmd/helpers.go	81.81% <ø> (ø)
... and 74 more

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[kevgo]

Blocking on shipping ory/cli#239 as a new Ory CLI version.