change user_name still used as login and add display_name for dashboard view instead of username on login

backend/database/erd_schema.sql

@@ -25,10 +25,10 @@
 CREATE TABLE IF NOT EXISTS user_access (
     user_id         SERIAL PRIMARY KEY,
     user_name       VARCHAR(30)  NOT NULL UNIQUE,
+    display_name    VARCHAR(30)  NOT NULL UNIQUE,
     password        VARCHAR(128) NOT NULL,
     last_login      TIMESTAMP WITH TIME ZONE,
     is_superuser    BOOLEAN      NOT NULL DEFAULT FALSE,
-    is_staff        BOOLEAN      NOT NULL DEFAULT FALSE,
     is_active       BOOLEAN      NOT NULL DEFAULT TRUE,
     created_at      TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,
     updated_at      TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,