Feat/request context

[samwelkanda]

Overview

This PR attaches a request context object to the native Http Request object, or Graph Request Object, to control the behavior of middleware in the Python SDK.  A request context contains data that is persisted throughout the request and includes a ClientRequestId property, MiddlewareControl property to control behavior of middleware   as well as a FeatureUsage  property to keep track of middleware used in making the request. The request context is also be accessible to middleware components to override the options provided during middleware instantiation.

Demo

Sample usage by telemetry handler to add specific headers

client_request_id = request.context.client_request_id  
feature_usage = request.context.feature_usage  

request.headers.update({'client-request-id': f'{client_request_id}'})  
request.headers.update({'feature-usage': '{feature_usage}'})  
request.headers.update({'sdkVersion':   
           f 'graph-python-core/{SDK_VERSION} (featureUsage=feature_usage)'})

Notes

This design uses keyword arguments to pass request-specific options to middleware as opposed to a middleware options dictionary. Consequently, this means that per-request config for custom middleware is not supported for now.

Testing Instructions

• Pull the feat/request-context branch
• Instantiate a client and make a call to the graph api e.g

resp = client.get('/me')

• Observe that a context object was attached to the original request, and has the required properties

print(resp.request.context)
print(resp.request.context.client_request_id)
print(resp.request.context.feature_usage)

Fixes #79
Fixes #59
Fixes #43
Fixes #17

[MIchaelMainer]

@samwelkanda Besides the questions above, what else do we need to do on this PR? Do we need to re-review with the design changes?