- This adds a new `suffix` keyword arg to the `seq` function to allow
  the concatenation of a common suffix string onto a generated `seq`
  value.
- This 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.
- This also adds unit tests for the new keyword argument behavior.

- This also adds that example field to the other `Customer`
  class examples throughout the docs.

… text sequence

- Also, change the str test case to use Person.email field (to better match
  the example mock data).

- Removes unused variable in test method

- Changes made based on code review suggestions