soroban-rpc: doesn't allow content-type charset=utf8

[leighmcculloch]

What version are you using?

20.0.0-rc4 bce5e56

What did you do?

Make a request with the Content-Type header set to application/json; charset=utf-8.

What did you expect to see?

The same output as when Content-Type: application/json is provided:

❯ curl -v -s http://localhost:8000/soroban/rpc \
  --request POST \
  --header "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":"", "method":"getHealth"}'
*   Trying 127.0.0.1:8000...
* Connected to localhost (127.0.0.1) port 8000 (#0)
> POST /soroban/rpc HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/8.1.2
> Accept: */*
> Content-Type: application/json
> Content-Length: 47
> 
< HTTP/1.1 200 OK
< Server: nginx/1.18.0 (Ubuntu)
< Date: Thu, 09 Nov 2023 20:02:54 GMT
< Content-Type: application/json
< Content-Length: 55
< Connection: keep-alive
< Accept-Post: application/json
< Vary: Origin
< Vary: Origin
< 
* Connection #0 to host localhost left intact
{"jsonrpc":"2.0","id":"","result":{"status":"healthy"}}%                         

What did you see instead?

$ curl -v -s http://localhost:8000/soroban/rpc \
  --request POST \
  --header "Content-Type: application/json; charset=utf-8" \
  --data '{"jsonrpc":"2.0","id":"", "method":"getHealth"}'
*   Trying 127.0.0.1:8000...
* Connected to localhost (127.0.0.1) port 8000 (#0)
> POST /soroban/rpc HTTP/1.1
> Host: localhost:8000
> User-Agent: curl/8.1.2
> Accept: */*
> Content-Type: application/json; charset=utf-8
> Content-Length: 47
> 
< HTTP/1.1 415 Unsupported Media Type
< Server: nginx/1.18.0 (Ubuntu)
< Date: Thu, 09 Nov 2023 20:01:51 GMT
< Content-Length: 0
< Connection: keep-alive
< Accept-Post: application/json
< Vary: Origin
< Vary: Origin
< 
* Connection #0 to host localhost left intact