Panic when running giganto without --ca-certs option

[msk]

I'm experiencing a panic when running giganto version 0.21.0-alpha.2 (commit b8756ed) without providing the --ca-certs option.

Steps to reproduce:

1. Run giganto with the following command:

giganto -c config.toml --cert tests/certs/node1/cert.pem --key tests/certs/node1/key.pem

2. Observe the panic with the following error message:

thread 'main' panicked at src/publish.rs:73:34:
server configuration error with cert, key or root: no root trust anchors were provided

Config file:

My config.toml file contains the following:

log_dir = "log"
export_dir = "export"
data_dir = "data"

Stack backtrace:

Running with RUST_BACKTRACE=1 environment variable produces the following stack backtrace:

Stack backtrace:
   0: std::backtrace::Backtrace::create
   1: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
   2: giganto::server::config_server
   3: giganto::main::{{closure}}
   4: tokio::runtime::runtime::Runtime::block_on
   5: giganto::main
   6: std::sys::backtrace::__rust_begin_short_backtrace
   7: std::rt::lang_start::{{closure}}
   8: std::rt::lang_start_internal
   9: _main
stack backtrace:
   0: _rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::result::unwrap_failed
   3: giganto::main::{{closure}}
   4: tokio::runtime::runtime::Runtime::block_on
   5: giganto::main
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Expected behavior:

I expect giganto to handle the absence of the --ca-certs option more gracefully, perhaps by providing a more informative error message.