Bitcoin RPC not compatible with JSON-RPC 1.0

When calling Bitcoin RPC requests with 1.0 version, an error is returned:
```
> curl -d '{"jsonrpc": "1.0", "method":"getblockchaininfo","params":[],"id":1}' https://rpc-testnet.mydomain.xyz
/btc
{"jsonrpc":"2.0","id":1,"error":{"code":-32600,"message":"Unsupported JSON RPC version: 1.0"}}
```
This is problematic because many Bitcoin applications and protocols still use version 1.0 for legacy and compatibility reasons.
There should be an exception for Bitcoin upstreams, or an option to disable the check.