Webargs 8

[pzhang65]

Fixes #111

Relevant changes from webargs 5.x to 8.1:

• multiple locations are no longer supported in a single call, default location is json.
• allow use of unknown parameters on schemas.
• unknown is also settable by parser.*
• ValidationError messages are namespaced under the request location.

Changes to aiohttp-apispec:

• Bump webargs >= 8.0.1**
• Change all locations args to to location.
• Drop location kwargs backwards compatibility.
• Change all decorators schemas to use string for location instead of array.
• Add unit tests for unknown field validation.
• Update old tests to conform to new ValidationError messages.
• Fix test_register_route_for_relative_url().***

*Recommended TODO item to add ability to set an unknown behavior override for validation middleware. Just need to inject another argument to request body i.e., schema['unknown'] for parser to override unknown behavior defined in marshmallow schema.
**Since bumping webargs to >= 8.0.1 drops marshmallow 2 support, we should also consider bumping apispec to >=4.
***test_register_route_for_relative_url() was passing locally but failing in the pipeline. Upon closer inspection it looks like the assertion was incorrect. Adding url arg to setup should register a route so the routes_count_after_setup_apispec should not equal to routes_count before setup. Indeed after relevant fixes the test function is now passing both locally and should pass in CICD pipeline.

[lafrech]

Since bumping webargs to >= 8.0.1 drops marshmallow 2 support, we should also consider bumping apispec to >=4.

webargs / apispec maintainer, here.

When publishing a major webargs/apispec version, we generally drop support for the old one right away. But the migration is generally painless. webargs was an exception to this and I think we maintained 5.x for a little while.

Anyway, my point is go ahead and drop every non latest major version of webargs/apispec anytime. The former versions are unmaintained and it shouldn't bother anyone.

[maximdanilchenko]

@lafrech, thanks for the recommendation! I will drop all non latest versions of webargs and apispec soon.