initial working version of web server flow

src/error.rs

@@ -18,6 +18,14 @@ pub enum SalesforceAuthError {
 	#[error("invalid SFDX URL")]
 	InvalidSfdxUrl,
 
+	/// The OAuth callback request was invalid.
+	#[error("invalid OAuth callback")]
+	InvalidOAuthCallback,
+
+	/// The OAuth callback state did not match the generated state.
+	#[error("OAuth state mismatch")]
+	OAuthStateMismatch,
+
 	/// A URL failed to parse.
 	#[error("invalid URL `{url}`: {source}")]
 	InvalidUrl {
@@ -36,6 +44,10 @@ pub enum SalesforceAuthError {
 	#[error("HTTP error: {0}")]
 	Http(#[from] reqwest::Error),
 
+	/// I/O error returned while running the local OAuth callback server.
+	#[error("I/O error: {0}")]
+	Io(#[from] std::io::Error),
+
 	#[error("Token exchange failure: {0}")]
 	TokenExchange(String),