openapi-framework: add middleware for operations

[jjdonov]

The goal of this PR is to bring the functionality of args.operations up to speed with how args.paths works with regards to middleware.

While args.paths (autoload like functionality) allows you to expose an array of middleware as an operation handler, the args.operations requires that the operation handler be a function. Attempting to pass an array result in a TypeError

/path/to/project/node_modules/openapi-framework/dist/index.js:165
                                return innerFunction.bind({
                                                     ^

TypeError: innerFunction.bind is not a function

I believe this was first documented in #618, and can make mounting middleware awkward or impossible at times.

This PR is may me incomplete. If the maintainers are open to a change like this, then I'd love to take it across the finish line. However, since I'm relatively new to the codebase, I expect I may need some guidance.

• [x] I only have 1 commit.
• [x] My commit is prefixed with the relevant package (e.g. express-openapi: fixing something) Note: You can use the bin/commit script to automate this.
• [x] I have added tests.
• [x] I'm using the latest code from the master branch and there are no conflicts on my branch.
• [ ] I have added a suffix to my commit message that will close any existing issue my PR addresses (e.g. openapi-jsonschema-parameters: Adding examples to the validation keywords (fixes #455)).
• [x] My tests pass locally.
• [x] I have run linting against my code.

[jjdonov]

@jsdevel thanks for the merge 😄 hate to be a bother, but any idea when we might get a new version published? We have a lot of middleware work on the immediate horizon that this PR would help a ton with.

And in general, is there a roadmap/release calendar/similar available? We've become pretty heavy users of the library and would love to learn more about where its headed or ways to get involved!

[jsdevel]

soon @jjdonov