Feature/email support (#720)

* feat(frontend): ✨ add UI for testing email configuration

* feat(backend): ✨ add email service with common templates (WIP)

* test(backend): ✅ add basic tests for email configuration

* set defaults

* add email variables

Co-authored-by: Hayden <hay-kot@pm.me>

frontend/api/class-interfaces/email.ts

@@ -0,0 +1,28 @@
+import { BaseAPI } from "./_base";
+
+const routes = {
+  base: "/api/admin/email",
+};
+
+export interface CheckEmailResponse {
+  ready: boolean;
+}
+
+export interface TestEmailResponse {
+  success: boolean;
+  error: string;
+}
+
+export interface TestEmailPayload {
+  email: string;
+}
+
+export class EmailAPI extends BaseAPI {
+  check() {
+    return this.requests.get<CheckEmailResponse>(routes.base);
+  }
+
+  test(payload: TestEmailPayload) {
+    return this.requests.post<TestEmailResponse>(routes.base, payload);
+  }
+}