How to do it...

Let's create our model mixin:

1. Make sure to add "myproject.apps.core" to INSTALLED_APPS in the settings, because we want to take the templates directory into account for this module.
2. Add the following basic meta tag markup to meta_field.html:

{# templates/core/includes/meta_field.html #}
<meta name="{{ name }}" content="{{ content }}" />

3. Open the models.py file from the core package in your favorite editor, and add the following content:

# myproject/apps/core/models.py
from django.conf import settings
from django.db import models
from django.utils.translation import gettext_lazy as _
from django.utils.safestring import mark_safe
from django.template.loader import render_to_string


class MetaTagsBase(models.Model):
    """
    Abstract base class for generating meta tags
    """
    meta_keywords = models.CharField(
        _("Keywords"),
        max_length=255,
        blank=True,
        help_text=_("Separate keywords with commas."),
    )
    meta_description = models.CharField(
        _("Description"),
        max_length=255,
        blank=True,
    )
    meta_author = models.CharField(
        _("Author"),
        max_length=255,
        blank=True,
    )
    meta_copyright = models.CharField(
        _("Copyright"),
        max_length=255,
        blank=True,
    )

    class Meta:
        abstract = True

    def get_meta_field(self, name, content):
        tag = ""
        if name and content:
            tag = render_to_string("core/includes/meta_field.html", 
            {
                "name": name,
                "content": content,
            })
        return mark_safe(tag)

    def get_meta_keywords(self):
        return self.get_meta_field("keywords", self.meta_keywords)

    def get_meta_description(self):
        return self.get_meta_field("description", 
         self.meta_description)

    def get_meta_author(self):
        return self.get_meta_field("author", self.meta_author)

    def get_meta_copyright(self):
        return self.get_meta_field("copyright", 
         self.meta_copyright)

    def get_meta_tags(self):
        return mark_safe("\n".join((
            self.get_meta_keywords(),
            self.get_meta_description(),
            self.get_meta_author(),
            self.get_meta_copyright(),
        )))