Export metrics

[rhamzeh]

Checklist

• [X] I agree to the terms within the OpenFGA Code of Conduct.

Describe the problem you'd like to have solved

As a consumer of the SDK, I would like to hook it to my dashboards to get data on several metrics.

Describe the ideal solution

Integrate the OpenTelemetry Python API https://github.com/open-telemetry/opentelemetry-python/tree/main/opentelemetry-api (API docs)

Expose only from the inner OpenFgaApi. We need to be able to report the following metrics

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

And the metrics should have the following attributes associated with them

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 should create an overall meter for OpenFgaApi and then create counters, histograms as required for each metric we report.

For the semantically named attributes we can use the semantic conventions package https://pypi.org/project/opentelemetry-semantic-conventions/