Create a clean Koa application per request

[SantosGuillamot]

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This is part of the Server Extensibility feature. For full context please check out the final Implementation proposal.

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To make sure that we don't leak middleware and app configuration from one request to another, my proposal is to create a new Koa application in each request.

Right now this is our @frontity/core/src/server export:

const server = ({ packages }) => {
  // Create new app.
  const app = new Koa();

  // Configure the app...
  app.use(/* ... */);

  // Return the req/res function.
  return app.callback();
};

We should switch to something like this:

const server = ({ packages }) => (req, res) => {
  // Create a new app for each request.
  const app = new Koa();

  // Configure the app...
  app.use(/* ... */);

  // Return the final response.
  return app.callback()(req, res);
};

Dependencies: none.

Relevant code:

https://github.com/frontity/frontity/blob/dev/packages/core/src/server/index.tsx

[nicholasio]

Assigning this first task over to me, planning on working on this in the next few days.

[luisherranz]

Awesome 👏 👏 😄