feat(sso): introduce authentication with SAML

packages/backend/src/db/migrations/20230707094923_create_identities.ts

@@ -0,0 +1,17 @@
+import { Knex } from 'knex';
+
+export async function up(knex: Knex): Promise<void> {
+  return knex.schema.createTable('identities', (table) => {
+    table.uuid('id').primary().defaultTo(knex.raw('gen_random_uuid()'));
+    table.uuid('user_id').references('id').inTable('users');
+    table.string('remote_id').notNullable();
+    table.string('provider_id').notNullable();
+    table.string('provider_type').notNullable();
+
+    table.timestamps(true, true);
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  return knex.schema.dropTable('identities');
+}