module: Add rail_api.py & rail_api_enum.py

[chuanchan1116]

Pull request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [x] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Documentation content changes
• [ ] Other (please describe):

What is the current behavior?

Issue Number: N/A

What is the new behavior?

• Added python client for querying ticket fare for rail. This is aimed to integrate transport expense into the system

Other information

To use this module, one has to register OAUTH API key on https://tdx.transportdata.tw/ and export CLIENT_ID & CLIENT_SECRET to environment variable.

[chuanchan1116]

Since I haven't done the auth part so testing will failed, changing this to draft first.