WSGI request/response hooks

[owais]

Description

Replaced WSGI name callback with request/response hooks

Fixes #409

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• Added test case

Does This PR Require a Core Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

See contributing.md for styleguide, changelog guidelines, and more.

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[srikanthccv]

LGTM. I think one downside here is when a user has custom sampler which uses span name as a part of sampling decision then the default span name might not be really helpful. And any update_name calls can't change decision.

Updates the Span name. Upon this update, any sampling behavior based on Span name will depend on the implementation.

Note that Samplers can only consider information already present during span creation. Any changes done later, including updated span name, cannot change their decisions.

[lzchen]

custom sampler which uses span name as a part of sampling decision then the default span name might not be really helpful

I don't see a workaround for this? If this is needed in the future, name_callback might be needed.