Enhance UrlConstraints with allowed_hosts attribute.

[nimaxin]

Initial Checks

• I have searched Google & GitHub for similar requests and couldn't find anything
• I have read and followed the docs and still think this feature is missing

Description

Currently, Pydantic's UrlConstraints allows specifying allowed_schemes via the allowed_schemes parameter. However, there is no built-in mechanism to restrict Url validation to specific hosts.

I propose enhancing the UrlConstraints class in Pydantic by adding an allowed_hosts attribute. This attribute would allow users to specify a list of valid hosts for Url validation. The addition of the allowed_hosts attribute would provide users with more granular control over Url validation.

A demo of how code might look when setting the allowed_hosts parameter in UrlConstraints 👇

from typing import Annotated
from pydantic import BaseModel, HttpUrl, UrlConstraints

class Model(BaseModel):
    url: Annotated[HttpUrl, UrlConstraints(allowed_hosts=["www.github.com", "google.com"])]

Affected Components

• Compatibility between releases
• Data validation/parsing
• Data serialization - .model_dump() and .model_dump_json()
• JSON Schema
• Dataclasses
• Model Config
• Field Types - adding or changing a particular data type
• Function validation decorator
• Generic Models
• Other Model behaviour - model_construct(), pickling, private attributes, ORM mode
• Plugins and integration with other tools - mypy, FastAPI, python-devtools, Hypothesis, VS Code, PyCharm, etc.

[sydney-runkle]

@nimaxin,

Seems like a reasonable request. I believe we might be moving all of the annotated url types to concrete subclasses, so maybe we could add more support when we make that change, see #7353.