Add train station generator

[AngusDSR]

Motivation / Background

Currently, Faker doesn't have a train station generator, and this can be a problem for testing location-based applications or data pipelines that deal with transit data. Having a train station generator would add value to the Faker library and allow for more comprehensive testing of these types of applications.

Additional information

One alternative to adding a new train station generator would be to manually create a list of station names and use them in tests. However, this can be time-consuming and may not provide enough variety in the generated data.

Another alternative would be to use an external library or API to generate train station names, but this would add an additional dependency to the project and may not integrate well with Faker.

[thdaraujo]

nice, thanks for working on this! Left a few questions.

[AngusDSR]

For the Travel > TrainStations faker:

• added support for optional argument inputs
• added error handling
• allowed for case insensitivity
• extended testing to related to the above points
• Restructured YAML and code to give precedence to 'region' over 'type'

[thdaraujo]

good stuff, thanks for changing the code!

LGTM overall, but I left a few comments. I think we should keep it simple and not downcase the types and regions for now.

[AngusDSR]

• removed downcasing and symbol compatibility
• created #fill_missing_inputs_with_samples method and moved into private with #validate_arguments

[thdaraujo]

looks great!