plugin-client-redirects: Support external URLs

[matevz]

Have you read the Contributing Guidelines on issues?

• I have read the Contributing Guidelines on issues.

Description

We migrated a chapter describing the API from a plain markdown file into the project's source code API code comments. Then, we generated the API reference pages with the Solidity doc generator and host them on another domain (api.docs.oasis.io versus docs.oasis.io).

But, for backward compatibility, we always redirect any removed/renamed pages to a new URL using https://docusaurus.io/docs/api/plugins/@docusaurus/plugin-client-redirects. To make the redirect work in our case, we would need to use something like this:

        {
            to: 'https://api.docs.oasis.io/sol/sapphire-contracts/',
            from: '/dapp/sapphire/precompiles',
        },

, but this yields

[ERROR] ValidationError: "redirects[44].to" is not a valid pathname. Pathname should start with slash and not contain any domain or query string.

It would be nice to have support for redirecting to external websites. For now, we just use a placeholder file with "This chapter has beem moved to..." content.

Has this been requested on Canny?

No response

Motivation

See above.

API design

No response

Have you tried building it?

No response

Self-service

• I'd be willing to contribute this feature to Docusaurus myself.

[slorber]

Please respect our issue template, mention the docusaurus version used and always try on the latest version.

3.0 supports this: #9171