Enhance/auth-api

[nifedara]

What does this PR do?

Enhances documentation quality

• I added API description
• I removed trailing slashes from auth endpoints
• Contributes to resolving this issue: Enhance API documentation and examples hotosm/raw-data-api#219

Consideration?

• API description gives the consumer a summary of what the API does
• Having no trailing slashes is a good practice that ensures consistency in the endpoint urls

How to test?

• Clone this repo
• Follow Docker Installation Guide or local installation guide
• Shoot the server up and view the Documentation changes on your localhost