add chzzk chat handler, command handler

src/main/kotlin/space/mori/chzzk_bot/models/Command.kt

@@ -0,0 +1,21 @@
+package space.mori.chzzk_bot.models
+
+import org.jetbrains.exposed.dao.IntEntity
+import org.jetbrains.exposed.dao.IntEntityClass
+import org.jetbrains.exposed.dao.id.EntityID
+import org.jetbrains.exposed.dao.id.IntIdTable
+import org.jetbrains.exposed.sql.ReferenceOption
+
+object Commands: IntIdTable("commands") {
+    val user = reference("user", Users, onDelete = ReferenceOption.CASCADE)
+    val command = varchar("command", 255)
+    val content = text("content")
+}
+
+class Command(id: EntityID<Int>) : IntEntity(id) {
+    companion object : IntEntityClass<Command>(Commands)
+
+    var user by User referencedOn Commands.user
+    var command by Commands.command
+    var content by Commands.content
+}