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>

tests/unit_tests/test_email_service.py

@@ -0,0 +1,65 @@
+import pytest
+
+from mealie.core.config import AppSettings
+from mealie.services.email import EmailService
+from mealie.services.email.email_senders import ABCEmailSender
+
+FAKE_ADDRESS = "my_secret_email@email.com"
+
+SUBJECTS = {"Mealie Forgot Password", "Invitation to join Mealie", "Test Email"}
+
+
+class TestEmailSender(ABCEmailSender):
+    def send(self, email_to: str, subject: str, html: str) -> bool:
+
+        # check email_to:
+        assert email_to == FAKE_ADDRESS
+
+        # check subject:
+        assert subject in SUBJECTS
+
+        # check html is rendered:
+        assert "{{" not in html
+        assert "}}" not in html
+
+        return True
+
+
+def patch_env(monkeypatch):
+    monkeypatch.setenv("SMTP_HOST", "email.mealie.io")
+    monkeypatch.setenv("SMTP_PORT", 587)
+    monkeypatch.setenv("SMTP_TLS", True)
+    monkeypatch.setenv("SMTP_FROM_NAME", "Mealie")
+    monkeypatch.setenv("SMTP_FROM_EMAIL", "mealie@mealie.io")
+    monkeypatch.setenv("SMTP_USER", "mealie@mealie.io")
+    monkeypatch.setenv("SMTP_PASSWORD", "mealie-password")
+
+
+@pytest.fixture()
+def email_service(monkeypatch) -> EmailService:
+    patch_env(monkeypatch)
+    email_service = EmailService(TestEmailSender())
+    email_service.settings = AppSettings()
+    return email_service
+
+
+def test_email_disabled():
+    email_service = EmailService(TestEmailSender())
+    email_service.settings = AppSettings()
+    success = email_service.send_test_email(FAKE_ADDRESS)
+    assert not success
+
+
+def test_test_email(email_service):
+    success = email_service.send_test_email(FAKE_ADDRESS)
+    assert success
+
+
+def test_forgot_password_email(email_service):
+    success = email_service.send_forgot_password(FAKE_ADDRESS, "https://password-url.com")
+    assert success
+
+
+def test_invitation_email(email_service):
+    success = email_service.send_invitation(FAKE_ADDRESS, "https://invitie-url.com")
+    assert success