chore: apply license headers to all the source files

[feng-tao]

Summary of Changes

Per email discussions

Tests

What tests did you add or modify and why? If no tests were added or modified, explain why. Remove this line

Documentation

What documentation did you add or modify and why? Add any relevant links then remove this line

CheckList

Make sure you have checked all steps below to ensure a timely review.

• PR title addresses the issue accurately and concisely. Example: "Updates the version of Flask to v1.0.2"
  • In case you are adding a dependency, check if the license complies with the ASF 3rd Party License Policy.
• PR includes a summary of changes.
• PR adds unit tests, updates existing unit tests, OR documents why no test additions or modifications are needed.
• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
• PR passes make test

[codecov-commenter]

Codecov Report

Merging #41 into master will increase coverage by 0.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #41      +/-   ##
==========================================
+ Coverage   73.27%   73.50%   +0.22%     
==========================================
  Files           6        6              
  Lines         116      117       +1     
  Branches        8        8              
==========================================
+ Hits           85       86       +1     
  Misses         26       26              
  Partials        5        5              

Impacted Files	Coverage Δ
amundsen_common/log/action_log.py	85.71% <ø> (ø)
amundsen_common/log/action_log_callback.py	62.50% <ø> (+0.96%)	⬆️
amundsen_common/log/action_log_model.py	92.85% <ø> (ø)
amundsen_common/log/auth_caller_retrieval.py	0.00% <ø> (ø)
amundsen_common/log/caller_retrieval.py	80.00% <ø> (ø)
...mundsen_common/log/http_header_caller_retrieval.py	100.00% <ø> (ø)

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