Prevent invalid traceparent ("00-00000...") from being returned to the caller

[KarstenWintermann]

Signed-off-by: Karsten Wintermann 58027075+KarstenWintermann@users.noreply.github.com

Description

Added a check in http_channel.go which prevents an empty traceparent header from being returned to the caller.

This way, valid traceparent headers, which may be received from Kafka topics with raw payloads, are not overwritten.

Issue reference

Please reference the issue this PR will close: #7372

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Unit tests passing
• End-to-end tests passing
• Extended the documentation / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]
• Specification has been updated / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]
• Provided sample for the feature / Created issue in the https://github.com/dapr/docs/ repo: dapr/docs#[issue number]

[yaron2]

@KarstenWintermann see the linter failure

[KarstenWintermann]

@KarstenWintermann see the linter failure

OK, fixed it

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (21095cb) 62.24% compared to head (2b6c2e0) 62.23%.

Files	Patch %	Lines
pkg/channel/http/http_channel.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7406      +/-   ##
==========================================
- Coverage   62.24%   62.23%   -0.02%     
==========================================
  Files         240      240              
  Lines       22137    22138       +1     
==========================================
- Hits        13779    13777       -2     
- Misses       7208     7210       +2     
- Partials     1150     1151       +1     

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