This refactors all 8 serve protocols to use `rc.ParseOptions` for VFS
and protocol options decoding. It also implements parameter validation in the
main runner using `rc.CheckParamsUsed`.
- Update dlna, ftp, http, nfs, restic, s3, sftp, and webdav to call
rc.ParseOptions, enabling nested option block support.
- Remove unused configstruct imports.
- Update startRc in cmd/serve/rc.go to copy input parameters and
call rc.CheckParamsUsed to reject unknown parameters.
- Add TestRcStartFlatNestedAndUnknownRejection to cmd/serve/rc_test.go.
- Update inline documentation in serve/start command help to include
nested blocks information (vfsOpt, proxyOpt, opt) and a new WebDAV example.
Hakan İSMAİLandNick Craig-Wood