feat: imported users have importation date instead of registrataion date

- Now registration date is optional (we allow NULL) for imported users.
- And imported users have an importation date, which is NULL for
  registered users throught the sdantadrd registration process.

migrations/mysql/20221109092556_torrust_user_date_registered_allow_null.sql

@@ -0,0 +1 @@
+ALTER TABLE torrust_users CHANGE date_registered date_registered DATETIME NOT NULL

migrations/mysql/20221109095718_torrust_user_add_date_imported.sql

@@ -0,0 +1 @@
+ALTER TABLE torrust_users ADD COLUMN date_imported DATETIME DEFAULT NULL

migrations/sqlite3/20221109092556_torrust_user_date_registered_allow_null.sql

@@ -0,0 +1,11 @@
+CREATE TABLE IF NOT EXISTS torrust_users_new (
+    user_id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
+    date_registered TEXT DEFAULT NULL,
+    administrator BOOL NOT NULL DEFAULT FALSE
+);
+
+INSERT INTO torrust_users_new SELECT * FROM torrust_users;
+
+DROP TABLE torrust_users;
+
+ALTER TABLE torrust_users_new RENAME TO torrust_users

migrations/sqlite3/20221109095718_torrust_user_add_date_imported.sql

@@ -0,0 +1 @@
+ALTER TABLE torrust_users ADD COLUMN date_imported TEXT DEFAULT NULL

src/models/user.rs

@@ -3,7 +3,8 @@ use serde::{Deserialize, Serialize};
 #[derive(Debug, Serialize, Deserialize, Clone, sqlx::FromRow)]
 pub struct User {
     pub user_id: i64,
-    pub date_registered: String,
+    pub date_registered: Option<String>,
+    pub date_imported: Option<String>,
     pub administrator: bool,
 }
 
@@ -33,7 +34,8 @@ pub struct UserCompact {
 #[derive(Debug, Serialize, Deserialize, Clone, sqlx::FromRow)]
 pub struct UserFull {
     pub user_id: i64,
-    pub date_registered: String,
+    pub date_registered: Option<String>,
+    pub date_imported: Option<String>,
     pub administrator: bool,
     pub username: String,
     pub email: String,

src/upgrades/from_v1_0_0_to_v2_0_0/databases/sqlite_v2_0_0.rs

@@ -67,17 +67,17 @@ impl SqliteDatabaseV2_0_0 {
             })
     }
 
-    pub async fn insert_user(
+    pub async fn insert_imported_user(
         &self,
         user_id: i64,
-        date_registered: &str,
+        date_imported: &str,
         administrator: bool,
     ) -> Result<i64, sqlx::Error> {
         query(
-            "INSERT INTO torrust_users (user_id, date_registered, administrator) VALUES (?, ?, ?)",
+            "INSERT INTO torrust_users (user_id, date_imported, administrator) VALUES (?, ?, ?)",
         )
         .bind(user_id)
-        .bind(date_registered)
+        .bind(date_imported)
         .bind(administrator)
         .execute(&self.pool)
         .await

src/upgrades/from_v1_0_0_to_v2_0_0/upgrader.rs

@@ -3,7 +3,8 @@
 //! NOTES for `torrust_users` table transfer:
 //!
 //! - In v2, the table `torrust_user` contains a field `date_registered` non existing in v1.
-//!   It's used the day when the upgrade command is executed.
+//!   We changed that columns to allow NULL. WE also added the new column `date_imported` with
+//!   the datetime when the upgrader was executed.
 //! - In v2, the table `torrust_user_profiles` contains two new fields: `bio` and `avatar`.
 //!   Empty string is used as default value.
 
@@ -129,10 +130,10 @@ async fn transfer_user_data(
             &user.user_id, &user.username
         );
 
-        let default_data_registered = today_iso8601();
+        let date_imported = today_iso8601();
 
         let id = dest_database
-            .insert_user(user.user_id, &default_data_registered, user.administrator)
+            .insert_imported_user(user.user_id, &date_imported, user.administrator)
             .await
             .unwrap();