Refactor schedule and user repositories into modular structure

- Moved schedule repository logic into separate modules for SQLite and PostgreSQL implementations.
- Created a mapping module for shared data structures and mapping functions in the schedule repository.
- Added new mapping module for user repository to handle user data transformations.
- Implemented PostgreSQL and SQLite user repository adapters with necessary CRUD operations.
- Added tests for user repository functionality, including saving, finding, and deleting users.

k-tv-backend/domain/src/services/user.rs

@@ -0,0 +1,60 @@
+use std::sync::Arc;
+
+use uuid::Uuid;
+
+use crate::entities::User;
+use crate::errors::{DomainError, DomainResult};
+use crate::repositories::UserRepository;
+use crate::value_objects::Email;
+
+/// Service for managing users.
+pub struct UserService {
+    user_repository: Arc<dyn UserRepository>,
+}
+
+impl UserService {
+    pub fn new(user_repository: Arc<dyn UserRepository>) -> Self {
+        Self { user_repository }
+    }
+
+    pub async fn find_or_create(&self, subject: &str, email: &str) -> DomainResult<User> {
+        if let Some(user) = self.user_repository.find_by_subject(subject).await? {
+            return Ok(user);
+        }
+
+        if let Some(mut user) = self.user_repository.find_by_email(email).await? {
+            if user.subject != subject {
+                user.subject = subject.to_string();
+                self.user_repository.save(&user).await?;
+            }
+            return Ok(user);
+        }
+
+        let email = Email::try_from(email)?;
+        let user = User::new(subject, email);
+        self.user_repository.save(&user).await?;
+        Ok(user)
+    }
+
+    pub async fn find_by_id(&self, id: Uuid) -> DomainResult<User> {
+        self.user_repository
+            .find_by_id(id)
+            .await?
+            .ok_or(DomainError::UserNotFound(id))
+    }
+
+    pub async fn find_by_email(&self, email: &str) -> DomainResult<Option<User>> {
+        self.user_repository.find_by_email(email).await
+    }
+
+    pub async fn create_local(
+        &self,
+        email: &str,
+        password_hash: &str,
+    ) -> DomainResult<User> {
+        let email = Email::try_from(email)?;
+        let user = User::new_local(email, password_hash);
+        self.user_repository.save(&user).await?;
+        Ok(user)
+    }
+}