Core domain structure for harmony rs (#1)

Co-authored-by: jeangab <jeangabriel.gc@gmail.com>
Co-authored-by: Jean-Gabriel Gill-Couture <jeangabriel.gc@gmail.com>
Reviewed-on: johnride/harmony#1
Co-authored-by: jeangab <jg@nationtech.io>
Co-committed-by: jeangab <jg@nationtech.io>

harmony-rs/src/domain/executors/mod.rs

@@ -0,0 +1,30 @@
+use std::fmt;
+
+pub struct ExecutorResult {
+    message: String,
+}
+
+#[derive(Debug)]
+pub enum ExecutorError {
+    NetworkError(String),
+    AuthenticationError(String),
+    ConfigurationError(String),
+    UnexpectedError(String),
+}
+
+impl fmt::Display for ExecutorError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ExecutorError::NetworkError(msg) => write!(f, "Network error: {}", msg),
+            ExecutorError::AuthenticationError(msg) => write!(f, "Authentication error: {}", msg),
+            ExecutorError::ConfigurationError(msg) => write!(f, "Configuration error: {}", msg),
+            ExecutorError::UnexpectedError(msg) => write!(f, "Unexpected error: {}", msg),
+        }
+    }
+}
+
+impl std::error::Error for ExecutorError {}
+
+pub trait SshClient {
+    fn test_connection(&self, username: String, password: String) -> Result<(), ExecutorError>;
+}