The email address of participant is added to all meetings, not just the one he joined. Django

Question

Followed the tutorial on creating meetups and allow participants join them. When adding a participant (his email address) using the form, the email address is added to all meetings, not just the one he joined. I am new to Django, but it seems like the problem is in the ManyToMany relationship.

Models.py

from django.db import models

class Location(models.Model):
    name = models.CharField(max_length=200)
    address = models.CharField(max_length=300)

    def __str__(self):
        return f'{self.name} ({self.address})'


class Participant(models.Model):
    email = models.EmailField(unique=True)

    def __str__(self):
        return self.email


class Meetup(models.Model):
    title = models.CharField(max_length=200)
    organizer_email = models.EmailField()
    date = models.DateField()
    slug = models.SlugField(unique=True)
    description = models.TextField()
    image = models.ImageField(upload_to='images')
    location = models.ForeignKey(Location, on_delete=models.CASCADE)
    participants = models.ManyToManyField(Participant, blank=True)

    def __str__(self):
        return f'{self.title} - {self.slug}'

Views.py

from django.shortcuts import render, redirect

from .models import Meetup, Participant
from .forms import RegistrationForm

# Create your views here.

def index(request):
    meetups = Meetup.objects.all()
    return render(request, 'meetups/index.html', {
        'meetups': meetups
    })


def meetup_details(request, meetup_slug):
    try:
        selected_meetup = Meetup.objects.get(slug=meetup_slug)
        if request.method == 'GET':
            registration_form = RegistrationForm()
        else:
            registration_form = RegistrationForm(request.POST)
            if registration_form.is_valid():
                user_email = registration_form.cleaned_data['email']
                participant, _ = Participant.objects.get_or_create(email=user_email)
                selected_meetup.participants.add(participant)
                return redirect('confirm-registration', meetup_slug=meetup_slug)

        return render(request, 'meetups/meetup-details.html', {
                'meetup_found': True,
                'meetup': selected_meetup,
                'form': registration_form
            })
    except Exception as exc:
        return render(request, 'meetups/meetup-details.html', {
            'meetup_found': False
        })


def confirm_registration(request, meetup_slug):
    meetup = Meetup.objects.get(slug=meetup_slug)
    return render(request, 'meetups/registration-success.html', {
        'organizer_email': meetup.organizer_email
    })

Forms.py

from django import forms

class RegistrationForm(forms.Form):
    email = forms.EmailField(label='Your email')