Add Instana Propagator: Instana Propagator Extension

[HeenaBansal20]

Which problem is this PR solving?
This PR adds a vendor specific propagator for the vendor specific trace correlation headers used by Instana.

Short description of the changes
Add Instana propagator plus unit tests.

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• ✅ login: HeenaBansal20 / name: Heena Bansal (aa1ba39, 0cae628, 7acb45d, 8b5e91e, 7df2b96, 86f0a77)

[brettmc]

This looks like a good start - there are a few CI issues to fix (you can run all these checks locally, check out developer/contributing documentation)

[HeenaBansal20]

@brettmc , I have fixed the CI issues locally and hoping it will be fine in CI too, But I don't see CI checks gets triggered for the PR.
The deptrac reported the below violation on registry.php. However I do see that this is required and other propagators also uses to register their propagator class. I am not sure what needs to be done for this one.

Reason      Extension                                                                                            
----------- ----------------------------------------------------------------------------------------------------- 
 Violation   /src/Extension/Propagator/Instana/_register.php must not depend on OpenTelemetry\SDK\Registry (SDK)  
             /usr/src/myapp/src/Extension/Propagator/Instana/_register.php:7                                      
 Violation   /src/Extension/Propagator/Instana/_register.php must not depend on OpenTelemetry\SDK\Registry (SDK)  
             /usr/src/myapp/src/Extension/Propagator/Instana/_register.php:10                                     
----------- -----------------------------------------------------------------------------------------------------

Thanks

[Nevay]

This propagator must not be maintained in this repository, see Propagators Distribution:

Additional Propagators implementing vendor-specific protocols such as AWS
X-Ray trace header protocol MUST NOT be maintained or distributed as part of
the Core OpenTelemetry repositories.

[HeenaBansal20]

This propagator must not be maintained in this repository, see Propagators Distribution:

Additional Propagators implementing vendor-specific protocols such as AWS
X-Ray trace header protocol MUST NOT be maintained or distributed as part of
the Core OpenTelemetry repositories.

@Nevay , I understand that vendor-specific propagators are not maintained by the core opentelemetry-php maintainers. However, I noticed that the opentelemetry-js-contrib repository hosts an Instana propagator for Node.js, which inspired the idea to host the Instana propagator for PHP here as well.

That said, I’m happy to volunteer myself and my colleague as maintainers for this extension.

Since @brettmc expressed support for contributing the Instana propagator to this repository, I’ve gone ahead and submitted a PR.

Looking forward to your thoughts or suggestions.

[ChrisLightfootWild]

This propagator must not be maintained in this repository, see Propagators Distribution:

Additional Propagators implementing vendor-specific protocols such as AWS
X-Ray trace header protocol MUST NOT be maintained or distributed as part of
the Core OpenTelemetry repositories.

@Nevay , I understand that vendor-specific propagators are not maintained by the core opentelemetry-php maintainers. However, I noticed that the opentelemetry-js-contrib repository hosts an Instana propagator for Node.js, which inspired the idea to host the Instana propagator for PHP here as well.

That said, I’m happy to volunteer myself and my colleague as maintainers for this extension.

Since @brettmc expressed support for contributing the Instana propagator to this repository, I’ve gone ahead and submitted a PR.

Looking forward to your thoughts or suggestions.

The referenced contrib repo is https://github.com/open-telemetry/opentelemetry-php-contrib.

This PR is currently against the PHP Core repo, https://github.com/open-telemetry/opentelemetry-php and should thus be ported to contrib.

[HeenaBansal20]

This propagator must not be maintained in this repository, see Propagators Distribution:

Additional Propagators implementing vendor-specific protocols such as AWS
X-Ray trace header protocol MUST NOT be maintained or distributed as part of
the Core OpenTelemetry repositories.

@Nevay , I understand that vendor-specific propagators are not maintained by the core opentelemetry-php maintainers. However, I noticed that the opentelemetry-js-contrib repository hosts an Instana propagator for Node.js, which inspired the idea to host the Instana propagator for PHP here as well.
That said, I’m happy to volunteer myself and my colleague as maintainers for this extension.
Since @brettmc expressed support for contributing the Instana propagator to this repository, I’ve gone ahead and submitted a PR.
Looking forward to your thoughts or suggestions.

The referenced contrib repo is https://github.com/open-telemetry/opentelemetry-php-contrib.

This PR is currently against the PHP Core repo, https://github.com/open-telemetry/opentelemetry-php and should thus be ported to contrib.

Thanks @ChrisLightfootWild for suggestion. I agree this extension should be ported to opentelemetry-php-contrib. I'll move this PR there.
Thank you.

[HeenaBansal20]

Opened the PR under opentelemetry-php-contrib repo and Hence closing this one.
open-telemetry/opentelemetry-php-contrib#365