fix: unify login/logout dev routes for http servers

[emmenko]

This PR aims to fix an issue that we currently have with one of our internal apps, due to the new application config.

TL;DR: the login/logout dev pages that we use in the dev server and in the mc-http-server should only be used when the property disableAuthRoutesOfDevServer is explicitly passed or when the application is not running behind a proxy.

[changeset-bot]

🦋 Changeset is good to go

Latest commit: 567d3b5

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This PR includes changesets to release 6 packages

Name	Type
@commercetools-frontend/mc-dev-authentication	Patch
@commercetools-frontend/mc-http-server	Patch
@commercetools-frontend/mc-scripts	Patch
merchant-center-application-template-starter	Patch
playground	Patch
@commercetools-local/visual-testing-app	Patch

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[emmenko]

This was the original issue, where the disableAuthRoutesOfDevServer wasn't taken into account.

With the new config, the servedByProxy value is inferred from the node env or app env.
In the case of the auth app, when starting the app locally in production mode (NODE_ENV=production MC_APP_ENV=development), the servedByProxy is set to false, causing the dev login page to be rendered. However, for the auth app, we want to render the "real" login page and for that we need to use the disableAuthRoutesOfDevServer.

[tdeekens]

Looks good. Thanks for covering the edge case.