feat: add opentelemetry metrics reporting

[ewanharris]

Description

Introduces OpenTelemetry metrics reporting into the SDK for specific actions, we're intentionally starting with only a few metric events that we can then grow over time.

We don't have any formal documentation for this currently, we'll write this as we roll it out across all SDKs, so here is a summary of the events and the associated attributes:

Metric Name	Type	Description
fga-client.request.duration	Histogram	The total request time for FGA requests
fga-client.query.duration	Histogram	The amount of time the FGA server took to process the request
fga-client.credentials.request	Counter	The total number of times a new token was requested when using ClientCredentials

Attribute Name	Type	Description
fga-client.response.model_id	string	The authorization model ID that the FGA server used
fga-client.request.method	string	The FGA method/action that was performed
fga-client.request.store_id	string	The store ID that was sent as part of the request
fga-client.request.model_id	string	The authorization model ID that was sent as part of the request, if any
fga-client.request.client_id	string	The client ID associated with the request, if any
fga-client.user	string	The user that is associated with the action of the request for check and list users
http.status_code	int	The status code of the response
http.method	string	The HTTP method for the request
http.host	string	Host identifier of the origin the request was sent to

We're implementing this using the @opentelemetry/api which means that all actions will be a no-op unless a @opentelemetry/sdk-node (or equivalent) instance is configured within an application. This is currently in draft as we work through the implementation across SDKs but we're looking for any feedback folks may have!

References

Closes #108

Review Checklist

• [ x] I have clicked on "allow edits by maintainers".
• I have added documentation for new/changed functionality in this PR or in a PR to openfga.dev [Provide a link to any relevant PRs in the references section above]
• The correct base branch is being used, if not main
• I have added tests to validate that the change in functionality is working as expected

[jasehackman]

👋 Thank you for this work. There is a typo in the fga-client.request.client_id description. It says it provides the model id used when it should say the client id.

[ewanharris]

Ah thanks for the catch @jasehackman, updated to include the missing client id field

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.79245% with 7 lines in your changes missing coverage. Please review.

Project coverage is 83.48%. Comparing base (ee24c7d) to head (daf0206).
Report is 4 commits behind head on main.

Files	Patch %	Lines
telemetry.ts	76.47%	1 Missing and 3 partials ⚠️
common.ts	85.71%	1 Missing and 1 partial ⚠️
credentials/credentials.ts	83.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #117      +/-   ##
==========================================
- Coverage   83.57%   83.48%   -0.10%     
==========================================
  Files          18       19       +1     
  Lines         968     1005      +37     
  Branches      168      230      +62     
==========================================
+ Hits          809      839      +30     
- Misses         76       78       +2     
- Partials       83       88       +5     

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