Emulate routes config

[manekinekko]

Checkout docs for more details.

[aaronpowell]

With #11 I've implemented a first-pass on supporting this.

When the proxy starts up it'll look for a routes.json file in the app_artifact_location, and if it exists it'll load those routing rules into the proxy server. Then, when a request comes in, the proxy server will check if the route matches a rule. If a rule is found, the app which check what the rule states (access control, redirect or status code response), and then apply what the rule states.

[aaronpowell]

There's still a few outstanding things:

• Custom error pages
• Custom mime types
• Default headers
• Redirects (it won't send the right status code response)

[anthonychu]

With the new unified config file coming, perhaps we should pivot and support that instead of routes.json.

Also would be great if the emulator can search for the config file, starting from the app_location. Perhaps add an additional command line flag to specify the location of the file, as this info may not be available when starting using something like --use-app.

@mkarmark can provide info on the routing, fallback, and response overrides logic in the new config file.

[manekinekko]

Notes from today's meeting with Anthony Chu and Mitali Karmarkar:

• idea: we could publish the route engine as a binary and do a function call from within the CLI.