Add MessageSaver plugin. Fix some buggy queries.

migrations/1543053430712-CreateMessagesTable.ts

@@ -0,0 +1,72 @@
+import { MigrationInterface, QueryRunner, Table } from "typeorm";
+
+export class CreateMessagesTable1543053430712 implements MigrationInterface {
+  public async up(queryRunner: QueryRunner): Promise<any> {
+    await queryRunner.createTable(
+      new Table({
+        name: "messages",
+        columns: [
+          {
+            name: "id",
+            type: "bigint",
+            unsigned: true,
+            isPrimary: true
+          },
+          {
+            name: "guild_id",
+            type: "bigint",
+            unsigned: true
+          },
+          {
+            name: "channel_id",
+            type: "bigint",
+            unsigned: true
+          },
+          {
+            name: "user_id",
+            type: "bigint",
+            unsigned: true
+          },
+          {
+            name: "is_bot",
+            type: "tinyint",
+            unsigned: true
+          },
+          {
+            name: "data",
+            type: "mediumtext"
+          },
+          {
+            name: "posted_at",
+            type: "datetime(3)"
+          },
+          {
+            name: "deleted_at",
+            type: "datetime(3)",
+            isNullable: true,
+            default: null
+          },
+          {
+            name: "is_permanent",
+            type: "tinyint",
+            unsigned: true,
+            default: 0
+          }
+        ],
+        indices: [
+          { columnNames: ["guild_id"] },
+          { columnNames: ["channel_id"] },
+          { columnNames: ["user_id"] },
+          { columnNames: ["is_bot"] },
+          { columnNames: ["posted_at"] },
+          { columnNames: ["deleted_at"] },
+          { columnNames: ["is_permanent"] }
+        ]
+      })
+    );
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<any> {
+    await queryRunner.dropTable("messages");
+  }
+}