Cannot reliably depend on NOW_GITHUB_* environment variables.

[emmenko]

Ref #342

TL;DR: the Github ZEIT Now integration seems to alias the domain when a PR is merged to master. This makes sense on one side, because there are technically no changes, but as soon as we rely on NOW_GITHUB_* environment variables, we have a problem.

This is the case for things like rendering the cookie consent scripts.

commercetools-docs-kit/packages/gatsby-theme-docs/gatsby-ssr.js

Lines 16 to 18 in 40be3d6

	const isProduction = process.env.GATSBY_NODE_ENV === 'production';
	const isNowBuild = Boolean(process.env.GATSBY_NOW_GITHUB_DEPLOYMENT);
	const isMasterBranch = process.env.GATSBY_NOW_GITHUB_COMMIT_REF === 'master';

See:

• https://spectrum.chat/zeit/now/now-for-github-can-we-force-deployment-building-upon-merges-to-master~71a27bb7-1b6a-4fdd-bcc6-8d9f1c39f0c0
• Allow GitHub merges to trigger new builds even when no changes in code vercel/vercel#2407

We need to find a different solution for conditionally render elements or not, as we can't rely on those environment variables anymore.