Add support for suffix in seq (fix #93)

[timjklein36]

Add support for suffix in seq (fix #93)

What

This change introduces the ability to append a common suffix on to values generated by seq.

Fixes #93

Why

Some fields may represent data that generally contains a common suffix, like in the case of emails. Mock data is therefore differentiated in the first portion of the field's value. An example of this:

fake.user1@example.com
fake.user2@example.com
...

By allowing an optionally supplied suffix, the seq function is able to append some common string onto its generated values.

How

A suffix keyword argument was added to the seq function to allow the concatenation of a common suffix string onto a generated value. This will not work with types of value other than str. Tests have been added to cover the "happy" and some "sad" path use of the new keyword argument.

Example:

from django.db import models
from model_bakery.recipe import Recipe, seq


class Person(models.Model):
    email = models.CharField(max_length=50)


person_recipe = Recipe(Person, email=seq('fake.user', suffix='example.com')

person_recipe.make().email  # 'fake.user1@example.com'
person_recipe.make().email  # 'fake.user2@example.com'
person_recipe.make().email  # 'fake.user3@example.com'

This PR also adds a section under "Sequences in recipes" to the documentation to provide example usage of the new keyword argument. Additionally, an email field is added to the Customer example model in the README.md to go along with the new section in the documentation.

Note: the line altered in seq (shown below) takes into account that if no suffix argument is supplied, it will essentially append an un-initialized type of the same as the value input. For number types, this is equivalent to 0.

yield value + type(value)(n) + (suffix or type(value)())

[berinhard]

Thanks for such a clean, testable and documented PR @timjklein36! I left 2 suggestion on how we can improve the error handling for this new parameter. Besides that, I'm all good with the code and the PR.

I'll wait for @anapaulagomes or @amureki to review it and as soon as we have an extra approval we can merge this.

[timjklein36]

@berinhard I updated the code based on your suggestions. Take a look at your earliest convenience. Thanks!

[berinhard]

Looks great! Thanks =)

[anapaulagomes]

Thanks for your contribution, @timjklein36! This is a really nice feature for seq. 🌷

I left small comments but I'm not sure about the naming. I think end would fit better than suffix, only because we already have start as a parameter of seq. I'd love to hear your and @berinhard thoughts about it.

[berinhard]

Docstrings =)

[timjklein36]

@berinhard @anapaulagomes I added a seq docstring. Let me know if it suits your expectations. Thanks!

[anapaulagomes]

LGTM! 🎉

[berinhard]

Nice! Thanks =)