add edoxid calendar sync dag

Sync jadwal sidang eDOXID ke Google Calendar "Jadwal Sidang" tiap 5 menit
(read-only ke doxid2022), plus reminder email H-1/1-jam via Gmail API
karena reminder Calendar bawaan tidak ikut ke kalender pribadi attendee.

scripts/edoxid_calendar_gmail.py

@@ -0,0 +1,35 @@
+import base64
+from email.mime.text import MIMEText
+
+from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
+from googleapiclient.discovery import build
+
+from scripts.edoxid_calendar_config import GoogleConfig
+
+
+class GmailService:
+    """Kirim email reminder H-1/1-jam sebagai tu@informatika.untan.ac.id
+    langsung (scope gmail.send, akun OAuth yang sama dengan Calendar)."""
+
+    def __init__(self, config: GoogleConfig):
+        creds = Credentials(
+            token=None,
+            refresh_token=config.refresh_token,
+            token_uri="https://oauth2.googleapis.com/token",
+            client_id=config.client_id,
+            client_secret=config.client_secret,
+            scopes=["https://www.googleapis.com/auth/gmail.send"],
+        )
+        creds.refresh(Request())
+
+        self._service = build("gmail", "v1", credentials=creds, cache_discovery=False)
+
+    def send(self, to: list[str], subject: str, body_text: str) -> str:
+        message = MIMEText(body_text, "plain", "utf-8")
+        message["to"] = ", ".join(to)
+        message["subject"] = subject
+
+        raw = base64.urlsafe_b64encode(message.as_bytes()).decode("utf-8")
+        result = self._service.users().messages().send(userId="me", body={"raw": raw}).execute()
+        return result["id"]