Make protocol authentication optional behind a feature flag.

Currently, the `hyper` crate (dependency of `reqwest`) causes linker errors when
you attempt to compile a consumer of `steven_protocol` as a dylib. Compiling as
a dylib is not uncommon for quick iteration; notably popularized by the Bevy
game engine.

See rust-lang/rust#82151 (comment).

protocol/Cargo.toml

@@ -4,6 +4,12 @@ version = "0.0.1"
 authors = [ "Thinkofdeath <thinkofdeath@spigotmc.org>", "iceiix <ice_ix@protonmail.ch>" ]
 edition = "2021"
 
+[features]
+# Enables support for authenticating with Mojang servers.
+auth = ["reqwest"]
+
+default = ["auth"]
+
 [dependencies]
 serde = "1.0.132"
 serde_json = "1.0.73"
@@ -26,4 +32,4 @@ path = "../std_or_web"
 version = "0"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-reqwest = { version = "0.11.8", features = [ "blocking" ]}
+reqwest = { version = "0.11.8", features = [ "blocking" ], optional = true }

protocol/src/protocol/mod.rs

@@ -1019,6 +1019,7 @@ pub enum Error {
     Disconnect(format::Component),
     IOError(io::Error),
     Json(serde_json::Error),
+    #[cfg(feature = "auth")]
     #[cfg(not(target_arch = "wasm32"))]
     Reqwest(reqwest::Error),
 }
@@ -1035,6 +1036,7 @@ impl convert::From<serde_json::Error> for Error {
     }
 }
 
+#[cfg(feature = "auth")]
 #[cfg(not(target_arch = "wasm32"))]
 impl convert::From<reqwest::Error> for Error {
     fn from(e: reqwest::Error) -> Error {
@@ -1051,6 +1053,7 @@ impl ::std::fmt::Display for Error {
             Error::Disconnect(ref val) => write!(f, "{}", val),
             Error::IOError(ref e) => e.fmt(f),
             Error::Json(ref e) => e.fmt(f),
+            #[cfg(feature = "auth")]
             #[cfg(not(target_arch = "wasm32"))]
             Error::Reqwest(ref e) => e.fmt(f),
         }

protocol/src/protocol/mojang.rs

@@ -28,6 +28,7 @@ const LOGIN_URL: &str = "https://authserver.mojang.com/authenticate";
 const REFRESH_URL: &str = "https://authserver.mojang.com/refresh";
 const VALIDATE_URL: &str = "https://authserver.mojang.com/validate";
 
+#[cfg(feature = "auth")]
 #[cfg(not(target_arch = "wasm32"))]
 impl Profile {
     pub fn login(username: &str, password: &str, token: &str) -> Result<Profile, super::Error> {