Consider replacing oas-tools library as it appears abandoned

[mikelax]

Feature Overview

The Usher currently using the library oas-tools to perform various validations and quality-of-life improvements for taking an API First approach to application building. Unfortunately, it appears the library has been abandoned. The last release was over two years ago, and there are numerous security CVEs identified in it's dependencies that are not being addressed.

We should consider replacing oas-tools with a newer library, that is currently supported. Within the express ecosystem, I found express-openapi-validator, which appears to perform the same functions we are using from oas-tools.

✅ Request/Response Validation
✅ Security Middleware Validation
✅ Automatic mapping of Open API functions to express functions

Describe the solution you'd like
After reading over the project's readme, it seems it would be a fairly limited change to replace the libraries.
Small code updates in the main the-usher.js server set up, and replacing vendor extensions in the open api yaml file for the function mapping.

Additional context

Add any other context or screenshots about the feature request here.

[mikelax]

It's still worth considering if we should switch, but they did finally publish a new version in early March.

[mikelax]

The package has been getting support through 2022, with a major v3 release.
Here is the migration guide to update from v2 to v3.

As another datapoint, here are the npm trends for the two libraries.