Support query parameters and HTTP headers for API requests

[cam-schultz]

Context and scope
The relayer makes RPC requests to a handful of Avalanche APIs via the Golang clients. Specifically, the relayer uses:

• platformvm.Client
• info.Client

These clients support HTTP headers and query parameters in the form of the optional rpc.Option parameters to each of their method calls.

We should add query-parameters and http-headers fields to the top-level config to support these options. This would allow us to provide a rate limit bypass token, for example.

The relayer also uses ethclient.Client, which supports query parameters in the form of a fully specified URL. HTTP headers are supported via rpc.Client.SetHeader. It might make sense to add a query-parameters field to the source-subnets and destination-subnets lists for consistency.

[najeal]

Hi @cam-schultz , please assign it to me.

The values provided by the new fields need to be passed to every requests right?

[cam-schultz]

Hey @najeal, thanks for offering to take a look at this. @minghinmatthewlam is going to take an initial pass at this to support query parameters for p-chain-api-url and info-api-url to reach parity with the subnet RPC and WS API fields.

Please feel free to open a PR with any further proposed changes. To close this ticket out, we'll also need to support HTTP headers provided via configuration.

The values provided by the new fields need to be passed to every requests right?

For the Info API and P-Chain API calls, this is correct. The subnet RPC API takes a raw URL, so query parameters are directly supported. Further investigation needs to be done for supporting HTTP headers for subnet RPC calls.

[najeal]

@cam-schultz thank for the answer.
This means I need to wait for @minghinmatthewlam PR that will partially resolve the issue, then I can complete the rest?

[cam-schultz]

@najeal, yes that would be great. Appreciate your patience on this 🙏