feat: Added DiscordConfig for future usage

- Added crate::error::Error::IsNotImplemented
- Added Config::full_impl_path
- Added Config::discord_impl for discord crate

src/config/mod.rs

@@ -357,4 +357,19 @@ impl Config {
         path.push(self.map.clone());
         path
     }
+    
+    /// Returns full path to implementation config TOML, if defined
+    /// This path will be relative to working directory
+    /// Only makes sense if using inside binary crate,
+    /// which provides implementation config
+    pub fn full_impl_path(&self) -> Option<PathBuf> {
+        match &self.impl_path {
+            Some(impl_path) => {
+                let mut path = self.path.clone();
+                path.push(impl_path.clone());
+                Some(path)
+            },
+            None => None,
+        }
+    }
 }