Send email notification when lease starts or ends soon

Closes: #149

bin/lease_create_email.txt

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+Hi {project},
+
+We would like to inform you that your lease: {lease_uuid} has started. Below are the details of the lease:
+
+    - Lease Start Time: {start_time}
+    - Lease End Time: {end_time}
+    - Node Name: {node_name}
+    - Node UUID: {node_uuid}
+
+Best Regards,
+
+ESI Admin Team

bin/lease_expire_email.txt

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+Hi {project},
+
+We would like to inform you that your lease: {lease_uuid} will expire on {end_time}:
+
+    - Node Name: {node_name}
+
+To ensure the continuity of your data, please take the following steps:
+
+1. Save any important data associated with this resource.
+2. If you wish to extend your lease, please contact ESI admin team.
+
+Thank you!
+
+ESI Admin Team

bin/query_events.py

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+"""
+Description:
+This script is designed to query and send email notifications for ESI lease events.
+
+Usage:
+To run this script, execute it from CLI or add it to a scheduled task (like cronjob).
+Before running, ensure the following environment variables are set:
+    - ENABLE_EMAIL: Set to 'true' to enable email notifications. Default is 'false'.
+    - SMTP_SERVER: Hostname of the SMTP server for sending emails. Default is 'localhost'
+    - EMAIL_SENDER: The email address that will be used as the sender in outgoing emails
+    - LEASE_WARNING_DAYS: Number of days before a lease's end when a notification email should be sent
+    - LEASE_CREATE_TEMPLATE: File path to the email template for lease creation notifications
+    - LEASE_EXPIRE_TEMPLATE: File path to the email template for lease expiration warnings
+
+Example:
+$ python query_event.py
+"""
+
+import datetime
+from dateutil import parser
+from email.mime.multipart import MIMEMultipart
+from email.mime.text import MIMEText
+import json
+import os
+import subprocess
+import smtplib
+
+
+enable_email = os.getenv('ENABLE_EMAIL', 'false').lower() == 'true'
+smtp_server = os.getenv('SMTP_SERVER', 'localhost')
+email_sender = os.getenv('EMAIL_SENDER')
+lease_warning_days = int(os.getenv('LEASE_WARNING_DAYS', 1))
+lease_create_template = os.getenv('LEASE_CREATE_TEMPLATE', 'lease_create_email.txt')
+lease_expire_template = os.getenv('LEASE_EXPIRE_TEMPLATE', 'lease_expire_email.txt')
+
+
+def run_openstack_command(cmd):
+    output_json = subprocess.check_output('%s --format json' % cmd, shell=True)
+    return json.loads(output_json)
+
+def get_last_event_id(default_last_event_id=0, file_name='.esi-last-event-id'):
+    try:
+        with open(file_name, "r") as f:
+            last_event_id = int(f.read())
+    except FileNotFoundError:
+        last_event_id = default_last_event_id
+    except ValueError:
+        last_event_id = default_last_event_id
+    return last_event_id
+
+def write_last_event_id(last_event_id, file_name='.esi-last-event-id'):
+    with open(file_name, "w") as f:
+        f.write(str(last_event_id))
+
+def notify_lease(project_name, email_body):
+    try:
+        project = run_openstack_command('openstack project show %s' % project_name)
+        to_email = project.get('email')
+        if not to_email:
+            print('No email linked to project %s. '
+                  'Not sending email notification' % project)
+        else:
+            msg = MIMEMultipart()
+            msg['From'] = email_sender
+            msg['To'] = to_email
+            msg['Subject'] = '[ESI]Lease notification'
+            msg.attach(MIMEText(email_body, 'plain'))
+            server = smtplib.SMTP(smtp_server)
+            server.sendmail(email_sender, to_email,
+                            msg.as_string())
+            server.quit()
+            print("Email sent successfully to %s" % to_email)
+    except Exception as e:
+        print('Email not sent: %s: %s' %
+                (type(e).__name__, e))
+
+def fill_email_template(template_path, **kwargs):
+    try:
+        with open(template_path, 'r') as f:
+            content = f.read()
+            return content.format(**kwargs)
+    except FileNotFoundError:
+        print("email template path not found")
+
+def main():
+    last_event_id = get_last_event_id()
+    events = run_openstack_command('openstack esi event list --last-event-id %s' % last_event_id)
+    new_last_event_id = last_event_id
+    # checking for leases fulfillment
+    for event in events:
+        new_last_event_id = event['ID']
+        if event['Event Type'] == 'esi_leap.lease.fulfill.end':
+            node_uuid = event['Resource UUID']
+            lease_uuid = event['Object UUID']
+            lease = run_openstack_command('openstack esi lease show %s' % lease_uuid)
+            print("Lease %s with purpose %s on node %s started" % (lease_uuid, lease['purpose'], node_uuid))
+            if enable_email:
+                email_body_lease_start = fill_email_template(lease_create_template,
+                                                             project=lease['project'],
+                                                             lease_uuid=lease['uuid'],
+                                                             start_time=lease['start_time'],
+                                                             end_time=lease['end_time'],
+                                                             node_name=lease['resource'],
+                                                             node_uuid=lease['resource_uuid'])
+                notify_lease(lease['project'], email_body_lease_start)
+    write_last_event_id(new_last_event_id)
+
+    # Checking for leases expire soon
+    leases = run_openstack_command('openstack esi lease list --all')
+    now = datetime.datetime.utcnow()
+    for lease in leases:
+        lease_end = parser.parse(lease["End Time"])
+        if lease_end - now <= datetime.timedelta(lease_warning_days):
+            print('Lease %s is expiring in %s day(s)' %(lease["UUID"], lease_warning_days))
+            if enable_email:
+                email_body_lease_expire = fill_email_template(lease_expire_template,
+                                                              project=lease['Project'],
+                                                              lease_uuid=lease['UUID'],
+                                                              end_time=lease['End Time'],
+                                                              node_name=lease['Resource'])
+                notify_lease(lease['Project'], email_body_lease_expire)
+
+if __name__ == "__main__":
+    main()