feat: define get_username trait for forge out port

src/auth/application/port/out/forge/get_username.rs

@@ -0,0 +1,32 @@
+use mockall::predicate::*;
+use mockall::*;
+
+use super::errors::*;
+use crate::auth::domain::OAuthAccessToken;
+
+#[automock]
+#[async_trait::async_trait]
+pub trait GetUsername: Send + Sync {
+    async fn get_username(&self, access_token: &OAuthAccessToken) -> OutForgePortResult<String>;
+}
+
+#[cfg(test)]
+pub mod tests {
+    use super::*;
+
+    use std::sync::Arc;
+
+    pub fn mock_get_username(username: String, times: Option<usize>) -> Arc<dyn GetUsername> {
+        let mut m = MockGetUsername::default();
+        if let Some(times) = times {
+            m.expect_get_username()
+                .times(times)
+                .returning(move |_| Ok(username.clone()));
+        } else {
+            m.expect_get_username()
+                .returning(move |_| Ok(username.clone()));
+        }
+
+        Arc::new(m)
+    }
+}