[NEW] www/py-flask-smorest: Flask/Marshmallow-based REST API framework

REST API framework built upon Flask and marshmallow.

• Serialization, deserialization and validation using marshmallow Schema
• Explicit validation error messages returned in response
• Database-agnostic
• OpenAPI (Swagger) specification automatically generated and exposed with ReDoc or Swagger UI
• Pagination
• ETag

WWW: https://github.com/marshmallow-code/flask-smorest

PR: 242611
Submitted by: Goran Mekić <meka@tilda.center>