Add base server

geneit_backend/src/constants.rs

@@ -0,0 +1,28 @@
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct SizeConstraint {
+    min: usize,
+    max: usize,
+}
+
+impl SizeConstraint {
+    pub fn new(min: usize, max: usize) -> Self {
+        Self { min, max }
+    }
+}
+
+#[derive(Debug, Clone, serde::Serialize)]
+pub struct StaticConstraints {
+    pub mail_len: SizeConstraint,
+    pub user_name_len: SizeConstraint,
+    pub password_len: SizeConstraint,
+}
+
+impl Default for StaticConstraints {
+    fn default() -> Self {
+        Self {
+            mail_len: SizeConstraint::new(5, 255),
+            user_name_len: SizeConstraint::new(3, 30),
+            password_len: SizeConstraint::new(8, 255),
+        }
+    }
+}