feat(cmd/goat): XRPC subcommand

[bleonard252]

This PR introduces a generic XRPC subcommand, which allows executing XRPC queries and procedures on your PDS, or via the atproto-proxy header (which is set with the --proxy flag). This should aid in the development of XRPC endpoints, and it may be helpful for power users.

NAME:
   goat xrpc - use an XRPC endpoint

USAGE:
   goat xrpc [command options] <nsid> [paramKey=paramValue...]

DESCRIPTION:
   Execute an XRPC query or procedure via your PDS. Procedure inputs should be provided via standard input (i.e. a pipe, or redirection with <).

OPTIONS:
   --proxy value            the service to proxy to, referred to by its DID and service ID
   --type value             the MIME type of the request body for a procedure (default: "application/json")
   --procedure, --post, -p  execute an XRPC procedure (POST request) (default: false)
   --query, -q, --get, -g   execute an XRPC query (GET request) (default: false)
   --help, -h               show help

I set procedure and query to be options instead of subcommands so that lexicon resolution can be added later. If a lexicon resolves for a given NSID, the lexicon will tell it which one (procedure or query) it needs to be.

[bleonard252]

I'm noticing that XrpcClient.Do seems to have poor error reporting. I think it should attempt to output the body in the error, if it's JSON or plaintext, and at least the status code. Right now it's just "retrying," and the error message is that it "gave up" after trying 4 times:

error: request failed: Post "https://puffball.us-east.host.bsky.network/xrpc/xyz.northwoodforum.hierarchy.createCategory": POST https://puffball.us-east.host.bsky.network/xrpc/xyz.northwoodforum.hierarchy.createCategory giving up after 4 attempt(s)

edit: it also sometimes just gives generic error messages for HTTP status codes like 400, 404, 403, 401:

error: XRPC ERROR 400: InvalidRequest: InvalidRequest

[bnewbold]

I've had something like this on my TODO list for a while! I haven't dug in super deep to your implementation here, but I really like the HTTPie "interface" and copied that in an earlier atproto CLI tool: https://gitlab.com/bnewbold/adenosine/-/blob/main/extra/adenosine.1.md