## Is your feature request related to a problem?

A user mentioned needing a feature to clone dashboards as they create the same dashboard multiple times, each for a different end-customer. Given that we are already planning on doing default / custom dashboards (#1659) we can add this functionality to facilitate dashboard creation.

## Describe the solution you'd like

Simple functionality to duplicate a dashboard.
- Add "Duplicate" button to dashboard list and clone dashboard (e.g. "Copy - AARRR").
![screenshot](https://user-images.githubusercontent.com/5864173/93866745-fce46100-fcbf-11ea-8c96-b1acfb1981d5.png)


## Describe alternatives you've considered
Re-create the dashboard manually.


## Additional context
No additional context.


#### *Thank you* for your feature request – we love each and every one!

posthog/api/dashboard.py
import secrets
from typing import Any, Dict, Optional
import posthoganalytics
from django.db.models import Model, Prefetch, QuerySet
from django.db.models.query_utils import Q
from django.http import HttpRequest
from django.shortcuts import get_object_or_404
from django.utils.timezone import now
from django.views.decorators.clickjacking import xframe_options_exempt
from rest_framework import authentication, response, serializers, viewsets
from rest_framework.decorators import action
from rest_framework.permissions import IsAuthenticated
from rest_framework.request import Request
from sentry_sdk.api import capture_exception
from posthog.api.routing import StructuredViewSetMixin
from posthog.api.shared import UserBasicSerializer
from posthog.auth import PersonalAPIKeyAuthentication, PublicTokenAuthentication
from posthog.helpers import create_dashboard_from_template
from posthog.models import Dashboard, DashboardItem, Team
from posthog.permissions import ProjectMembershipNecessaryPermissions, TeamMemberAccessPermission
from posthog.tasks.update_cache import update_dashboard_item_cache, update_dashboard_items_cache
from posthog.utils import get_safe_cache, render_template, str_to_bool
class DashboardSerializer(serializers.ModelSerializer):