Create initial project structure

The initial project structure includes the base scaffolding of the
application as well as the ability to fetch the repo list from the
remote endpoint.

src/error.rs

@@ -0,0 +1,71 @@
+#![allow(clippy::enum_variant_names)]
+use thiserror::Error;
+
+/// The common error type for this Application.
+#[derive(Error, Debug)]
+pub enum DredgeError {
+    /// An error related to the configuration of the program.
+    #[error(transparent)]
+    ConfigError(#[from] ConfigError),
+
+    /// An error communicating with the Registry API
+    #[error(transparent)]
+    ApiError(#[from] ApiError),
+}
+
+/// An error related to the configuration fo the program.
+#[derive(Error, Debug)]
+pub enum ConfigError {
+    /// An error parsing the configuration from disk.
+    #[error("Failed to parse configuration file")]
+    ParseError(Box<dyn std::error::Error>),
+
+    /// An error writing the configuration to disk.
+    #[error("Failed to write configuration data")]
+    WriteError(Box<dyn std::error::Error>),
+
+    /// A generic IOError
+    #[error(transparent)]
+    IOError(#[from] std::io::Error),
+}
+
+impl From<toml::ser::Error> for ConfigError {
+    fn from(other: toml::ser::Error) -> Self {
+        Self::WriteError(Box::from(other))
+    }
+}
+
+impl From<toml::de::Error> for ConfigError {
+    fn from(other: toml::de::Error) -> Self {
+        Self::ParseError(Box::from(other))
+    }
+}
+
+impl From<xdg::BaseDirectoriesError> for ConfigError {
+    fn from(other: xdg::BaseDirectoriesError) -> Self {
+        Self::WriteError(Box::from(other))
+    }
+}
+
+/// An error related to the communication with the registry API.
+#[derive(Error, Debug)]
+pub enum ApiError {
+
+    /// Error parsing a URL
+    #[error(transparent)]
+    UrlParseError(#[from] url::ParseError),
+
+    /// Error in HTTP Request
+    #[error(transparent)]
+    HttpError(#[from] reqwest::Error),
+
+    #[error("Failed to parse response headers")]
+    ResponseHeaderParseError(Box<dyn std::error::Error>),
+}
+
+impl From<reqwest::header::ToStrError> for ApiError {
+
+    fn from(other: reqwest::header::ToStrError) -> Self {
+        Self::ResponseHeaderParseError(Box::from(other))
+    }
+}