Implement missing features, some cleanup

src/error.rs

@@ -2,12 +2,55 @@ use std::error::Error;
 use std::fmt;
 use std::fmt::Display;
 
+#[derive(Default, Debug)]
+pub struct ConfigParseError {
+    pub(crate) config_key: String,
+}
+
+impl Error for ConfigParseError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        None
+    }
+}
+
+// Implement std::fmt::Display for AppError
+impl Display for ConfigParseError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Couldn't parse value from string for key: {}",
+            self.config_key
+        ) // user-facing output
+    }
+}
+
+#[derive(Default, Debug)]
+pub struct MissingConfigError {
+    pub(crate) config_key: String,
+}
+
+impl Error for MissingConfigError {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        None
+    }
+}
+
+// Implement std::fmt::Display for AppError
+impl Display for MissingConfigError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
+            "Couldn't find required configuration option: {}",
+            self.config_key
+        ) // user-facing output
+    }
+}
+
 #[derive(Default, Debug)]
 pub struct NoQdiscFoundError;
 
 impl Error for NoQdiscFoundError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
-        // The compiler transparently casts `&sqlx::Error` into a `&dyn Error`
         None
     }
 }
@@ -24,7 +67,6 @@ pub struct PingParseError;
 
 impl Error for PingParseError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
-        // The compiler transparently casts `&sqlx::Error` into a `&dyn Error`
         None
     }
 }