change pw_cost to integer to match official impl

migrations/2020-02-20-085623_create_user/up.sql

@@ -2,7 +2,7 @@ CREATE TABLE users (
     id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
     email VARCHAR NOT NULL,
     password VARCHAR NOT NULL,
-    pw_cost VARCHAR NOT NULL,
+    pw_cost INTEGER NOT NULL,
     pw_nonce VARCHAR NOT NULL,
     version VARCHAR NOT NULL
 )

src/api.rs

@@ -81,7 +81,7 @@ fn _sign_in(db: DbConn, mail: &str, passwd: &str) -> Custom<JsonResp<AuthResult>
 
 #[derive(Serialize)]
 struct AuthParams {
-    pw_cost: String,
+    pw_cost: i32,
     pw_nonce: String,
     version: String
 }

src/schema.rs

@@ -17,7 +17,7 @@ table! {
         id -> Integer,
         email -> Text,
         password -> Text,
-        pw_cost -> Text,
+        pw_cost -> Integer,
         pw_nonce -> Text,
         version -> Text,
     }

src/user.rs

@@ -66,7 +66,7 @@ struct UserQuery {
     pub id: i32,
     pub email: String,
     pub password: String,
-    pub pw_cost: String,
+    pub pw_cost: i32,
     pub pw_nonce: String,
     pub version: String
 }
@@ -91,7 +91,7 @@ pub struct User {
     pub id: i32,
     pub email: String,
     pub password: Password,
-    pub pw_cost: String,
+    pub pw_cost: i32,
     pub pw_nonce: String,
     pub version: String
 }
@@ -101,7 +101,7 @@ pub struct User {
 pub struct NewUser {
     pub email: String,
     pub password: String,
-    pub pw_cost: String,
+    pub pw_cost: i32,
     pub pw_nonce: String,
     pub version: String
 }