feat: add user role database table and role-based permissions

src/main/resources/db/migration/mariadb/V0_3_0__UserRoles.sql

@@ -0,0 +1,7 @@
+CREATE TABLE IF NOT EXISTS user_role
+(
+    id         int auto_increment primary key,
+    username   varchar(255)                     not null unique,
+    role       varchar(255)                     not null,
+    created_at datetime default utc_timestamp() not null
+);

src/main/resources/db/migration/postgresql/V0_3_0__UserRoles.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS user_role
+(
+    id         serial,
+    username   varchar(255)                           not null unique,
+    role       varchar(255)                           not null,
+    created_at timestamp with time zone default now() not null,
+    PRIMARY KEY (id)
+);