Improve logging and validation for license keys.

[jaffinito]

BEGIN_COMMIT_OVERRIDE
feat: Improve logging and validation for license keys. (#2982)
END_COMMIT_OVERRIDE

Description

Adds an additional warning when the agent receives a HTTP 401 Unauthorized response from the collector. This occurs when the key is not valid (for many reasons).

Expands the validation logic from the license key in DefaultConfiguration to:

• Still perform the checks once and save the value if one is found. If nothing is found save string.Empty to prevent further checks.
• Check for empty/missing keys
• Check if the value contains "license". Our default key and keys used in unit test use values that contain that word.
• Check if it is the correct length - 40 characters
• Check if the characters are valid for a key - ASCII characters from 0x21 to 0x7E
• Check each of the different key locations and work through them in priority order to find a key without issues.
  • When a location has a value, but that value is invalid log a Warn message letting you know that a bad key was found and where.
  • If a valid key is found, report a Info message including where. Happens once since value is cached.
  • If no valid key is found log a Warn message to let us know. Happens each time the key is request from config.

Unit tests have been expanded to cover the new logic.

Note: valid in this context means that it is not null or whitespace, exactly 40 ASCII characters from 0x21 to 0x7E, or string contains "license" (case insensitive)).

Fixes #2969
Fixes #2783

Author Checklist

• Unit tests, Integration tests, and Unbounded tests completed
• Performance testing completed with satisfactory results (if required)

Reviewer Checklist

• Perform code review
• Pull request was adequately tested (new/existing tests, performance tests)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.17%. Comparing base (15f88c7) to head (6c36735).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2982      +/-   ##
==========================================
- Coverage   82.19%   82.17%   -0.02%     
==========================================
  Files         473      473              
  Lines       30362    30391      +29     
  Branches     3388     3392       +4     
==========================================
+ Hits        24955    24975      +20     
- Misses       4606     4617      +11     
+ Partials      801      799       -2     

Flag	Coverage Δ
Agent	83.15% <100.00%> (-0.02%)	⬇️
Profiler	73.13% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...c/Agent/Core/Configuration/DefaultConfiguration.cs	89.90% <100.00%> (+0.15%)	⬆️
...elic/Agent/Core/DataTransport/ConnectionManager.cs	78.14% <100.00%> (+0.59%)	⬆️

... and 3 files with indirect coverage changes

[chynesNR]

Very nice!