Create client to establish connection with discord and add basic framework with sample command

cipher_core/src/lib.rs

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+pub mod repository;

cipher_core/src/repository/mod.rs

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+use std::fmt::Display;
+
+use user_repository::UserRepository;
+
+pub mod user_repository;
+
+#[async_trait::async_trait]
+pub trait RepositoryProvider {
+    type BackendError: std::error::Error;
+
+    type Repository<'a>: Repository<BackendError = <Self as RepositoryProvider>::BackendError> + Send + Sync
+    where
+        Self: 'a;
+
+    async fn get(&self) -> Result<Self::Repository<'_>, RepositoryError<Self::BackendError>>;
+}
+
+pub trait Repository
+where
+    Self: UserRepository<BackendError = <Self as Repository>::BackendError>,
+{
+    type BackendError: std::error::Error;
+}
+
+#[derive(Debug)]
+pub struct RepositoryError<E>(pub E);
+
+impl<E> Display for RepositoryError<E>
+where
+    E: Display,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}

cipher_core/src/repository/user_repository.rs

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+use super::RepositoryError;
+
+#[async_trait::async_trait]
+pub trait UserRepository {
+    type BackendError: std::error::Error;
+
+    async fn user(&mut self, id: i32) -> Result<Option<User>, RepositoryError<Self::BackendError>>;
+
+    async fn insert_user(&mut self, new_user: NewUser) -> Result<User, RepositoryError<Self::BackendError>>;
+
+    async fn update_user(&mut self, user: User) -> Result<Option<User>, RepositoryError<Self::BackendError>>;
+
+    async fn remove_user(&mut self, id: i32) -> Result<Option<User>, RepositoryError<Self::BackendError>>;
+}
+
+pub struct User {
+    pub id: i32,
+    pub discord_user_id: u64,
+    pub pokemon_go_code: Option<String>,
+    pub pokemon_pocket_code: Option<String>,
+    pub switch_code: Option<String>,
+}
+
+pub struct NewUser {
+    pub discord_user_id: u64,
+    pub pokemon_go_code: Option<String>,
+    pub pokemon_pocket_code: Option<String>,
+    pub switch_code: Option<String>,
+}