Function generate_server_trait 

pub fn generate_server_trait(service: &ServiceDef) -> Result<TokenStream>

Generate server trait for a service

Example output:

#[async_trait::async_trait]
pub trait UserService: Send + Sync {
    type Error: Into<synapse_rpc::ServiceError> + Send;
    async fn get_user(&self, request: GetUserRequest) -> Result<GetUserResponse, Self::Error>;
    async fn create_user(&self, request: CreateUserRequest) -> Result<CreateUserResponse, Self::Error>;
}