Implement confirm user functionality

This commit adds the necessary functionality to confirm a user's account.

It includes the addition of a new column in the user table to track whether an account is confirmed or not, and the implementation of JWT for confirmation tokens.

This commit integrates the SparkPost API as well as React Email to send dynamic emails for whatever purpose.

Upon user registration, a confirmation email will be sent to the user.

config/sparkpost/client.ts

@@ -0,0 +1,11 @@
+import SparkPost from 'sparkpost';
+
+const { SPARKPOST_API_KEY } = process.env;
+
+if (!SPARKPOST_API_KEY) {
+  throw new Error('SPARKPOST_API_KEY is not defined');
+}
+
+const client = new SparkPost(SPARKPOST_API_KEY);
+
+export default client;