Allow formatting of flow parameter documentation strings

[tjordahl]

Describe the current behavior

Currently the docstring of (e.g.) enum parameters is dumped on to the UI as one long string. This makes it hard to self-document flow parameters for people running flows.

Example:

from pydantic import BaseModel

from prefect import flow


class BadParams(BaseModel):
    """This is a realllllly long description that should be rendered as markdown


    Attributes:
        a: This is a really long description that should be rendered as markdown
        b: This is a really long description that should be rendered as markdown
        c: This is a really long description that should be rendered as markdown
        x: This is a really long description that should be rendered as markdown
        y: This is a really long description that should be rendered as markdown
        z: This is a really long description that should be rendered as markdown
    """

    a: int
    b: int
    c: int
    x: int
    y: int
    z: int


@flow
def bad_params_render(params: BadParams):
    pass


if __name__ == "__main__":
    bad_params_render.serve()

Describe the proposed behavior

Support some sort of formatting, Markdown would be the obvious choice, to allow flow developers to nicely format this text.

Example Use

No response

Additional context

Prefect slack thread from 2024-09-13:
https://prefect-community.slack.com/archives/C0192RWGJQH/p1726235752005299