Fix warnings generated by clippy

shvcall: Avoid redundant references in `send_request` arguments

Bypass clippy checks on uppercase constants in the chainpack module
and allow Access::from_str to return Option instead of Result as in
the definition of from_str in FromStr trait.

src/bin/shvcall.rs

@@ -272,7 +272,7 @@ async fn make_call(url: &Url, opts: &Opts) -> Result {
                             match parse_line(line) {
                                 Ok((path, method, param)) => {
                                     let rqid =
-                                        send_request(&mut *frame_writer, &path, &method, &param)
+                                        send_request(&mut *frame_writer, path, method, param)
                                             .await?;
                                     loop {
                                         let resp = frame_reader.receive_message().await?;

src/chainpack.rs

@@ -6,6 +6,7 @@ use std::collections::BTreeMap;
 use crate::reader::{Reader, ByteReader, ReadError, ReadErrorReason};
 use crate::rpcvalue::{Map, IMap};
 
+#[allow(clippy::upper_case_acronyms)]
 #[warn(non_camel_case_types)]
 #[allow(dead_code)]
 pub(crate) enum PackingSchema {

src/metamethod.rs

@@ -28,6 +28,8 @@ impl From<u8> for Flag {
 #[derive(Debug, Copy, Clone, PartialEq, PartialOrd)]
 pub enum Access { Browse = 0, Read, Write, Command, Config, Service, SuperService, Developer, Superuser }
 impl Access {
+    // It makes sense to return Option rather than Result as the `FromStr` trait does.
+    #[allow(clippy::should_implement_trait)]
     pub fn from_str(value: &str) -> Option<Self> {
         match value {
             "bws" => Some(Access::Browse),