feature: add support for auth-protected subgraph query URLs

[Jannis]

This allows to configure a bearer auth token for the network and escrow subgraphs, in case that is required for the endpoint used.

[gusinacio]

Hey Jannis, thanks for contributing.

I'm assuming here that this PR is due to the shutdown of the hosted service.

The decentralized network exposes a way to embed the Api Key in the URL, would this still be necessary or is there any other case I'm missing?

[Jannis]

Hey Jannis, thanks for contributing.

I'm assuming here that this PR is due to the shutdown of the hosted service.

The decentralized network exposes a way to embed the Api Key in the URL, would this still be necessary or is there any other case I'm missing?

Indexers should be free to use whatever endpoints they want to query the network and escrow subgraphs. This change allows for instance to use endpoints that require an Authorization: Bearer ... header. An example would be another indexer with a free query auth token.