feat: use GITHUB_TOKEN if available in Serverless-Init .NET install script

[duncanpharvey]

Currently the .NET install script for Serverless-Init makes unauthenticated requests to the Github API, sometimes resulting in rate limiting. This PR adds a GITHUB_TOKEN to be passed as a Docker secret to the .NET install script to allow for an increased rate limit. If no GITHUB_TOKEN is passed then requests will be unauthenticated as they were before this change.

Motivation

#734

Additional Notes

• Check if a GITHUB_TOKEN environment variable is set. If it is, pass it in the Authorization header with Bearer
• Add a status_code attribute to the response json and print it for troubleshooting
• Use jq to parse the response json
  • Note that control characters needed to be stripped from the Github responses in order to be successfully parsed
• If the tracer version is not parsed from the response json, presumably due to rate limiting or some other issue on Github's end, exit the script

Github token provided -> success

#16 6.759 Github token provided
#16 7.243 Status code of version request: 200
#16 7.291 Downloading version 3.21.0 of the .NET tracer into /tmp/datadog-dotnet-apm.tar.gz
#16 7.291 Github token provided
#16 10.08 Status code of download request: 200

No Github token provided -> success

#16 7.664 Github token not provided
#16 7.967 Status code of version request: 200
#16 8.018 Downloading version 3.21.0 of the .NET tracer into /tmp/datadog-dotnet-apm.tar.gz
#16 8.019 Github token not provided
#16 11.10 Status code of download request: 200

No Github token provided -> rate limited

6.518 Github token not provided
6.780 Status code of version request: 403
6.828 Error: Could not determine the tracer version. Exiting.

Usage

• In the Dockerfile, read the value of the github-token secret into the GITHUB_TOKEN environment variable so it can be passed in the authentication header of the Github API request.

RUN --mount=type=secret,id=github-token,env=GITHUB_TOKEN \
    chmod +x /app/dotnet.sh && /app/dotnet.sh

• Pass value in GITHUB_TOKEN environment variable to the Docker secret github-token.

docker build -t <image> --secret id=github-token,env=GITHUB_TOKEN .

Relevant documentation to update following this change:

• https://docs.datadoghq.com/serverless/guide/gcr_serverless_init/?tab=dotnet
• https://docs.datadoghq.com/serverless/guide/aca_serverless_init/?tab=dotnet
• https://docs.datadoghq.com/serverless/guide/azure_app_service_linux_containers_serverless_init/?tab=dotnet

[janpieterz]

@duncanpharvey Amazing, thank you! Would you be able to ping me when the docker image is updated? We're now passing down the GITHUB_TOKEN so it should be visible relatively quick on our end.