Ensure path parameters are declared in each Operation

[mbuhot]

Paths.from_router now returns an :ok/:error tuple.
The error case will occur if any operation fails to declare a path parameter that is present in the phoenix route.

Fixes #52

@fenollp Is a breaking API change the way to go for this one? We could alternatively let it raise an error without changing the return type of the function.

[moxley]

Looks great. It would be preferred to keep Plug syntax for route paths, and to use Plug's built-in path parsing function, but I understand if that's not feasible.

[fenollp]

I agree with @moxley that this should defer to Plug for path parsing.
Also I’d say this doesn’t warrant a major version bump since this is a bugfix. I think the API should stay as before and just throw when encountering unexpected paths.

This would fail at compile time, right?

[moxley]

@fenollp:

Also I’d say this doesn’t warrant a major version bump since this is a bugfix.

It's a breaking API change. The bug doesn't seem directly related to the part of the API that has changed. But I don't know. I'm no expert at determining what constitutes a major version bump.

Perhaps a new function could be introduced that has the new behavior, and the old function could raise a warning?