support preflight OAuth in embeds

[mayakoneval]

Use this coe as an inbetween, so the parent page is making the request to the oauth url, redirect happens to the embed href, the embed href grabs the query params, pms to the parent page & the parent page pms to the embedded iframe

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: 13d0831300e993708ebbd68dc4624bd80c0cbd35

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

| Name | Type | | ---------------- | ----- | | @apollo/explorer | Minor | | @apollo/sandbox | Minor |

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[codesandbox-ci[bot]]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 13d0831300e993708ebbd68dc4624bd80c0cbd35:

Sandbox	Source
npm-embeddable-explorer (forked)	Configuration
npm-embeddable-sandbox	Configuration
maya-test-embed-next	Configuration
maya-test-embed-next	Configuration