[ENHANCEMENT] Improve ImageField error messaging to deal with paths, urls, none

[cceyda]

Is your feature request related to a problem? Please describe.
I'm already hosting my images independently. I don't wanna save he image inside the argilla dataset just the url... there currently doesn't seem to be a way to do this using ImageField (I was hoping this was what was meant by image support but ended up having to rollback to markdown hack again)

Describe the solution you'd like
ImageField should support urls

Describe alternatives you've considered
Use markdown

Additional context

[burtenshaw]

@cceyda Thanks for the issue. rg.ImageField already supports public urls, defined within the Record fields param. Do you have an example/error where you've tried this.

Here's the docs: https://docs.argilla.io/latest/reference/argilla/records/records/

[cceyda]

For rg.ImageField(name="image",required=False) & and a record with fields = { "image": "https://..."}
I got an error complaining about paths so I assumed:

File ~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/records/_resource.py:281, in <dictcomp>(.0)
    [280](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/records/_resource.py:280) def to_dict(self) -> dict:
--> [281](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/records/_resource.py:281)     return {key: cast_image(value) if self._is_image(key) else value for key, value in self.items()}

File ~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:80, in cast_image(image)
     [78](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:78)         return image
     [79](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:79)     else:
---> [80](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:80)         return filepath_to_data_uri(image)
     [81](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:81) elif isinstance(image, Path):
     [82](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:82)     return filepath_to_data_uri(image)

File ~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:59, in filepath_to_data_uri(file_path)
     [57](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:57) file_path = Path(file_path)
     [58](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:58) if file_path.exists():
---> [59](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:59)     with open(file_path, "rb") as image_file:
     [60](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:60)         img_str = base64.b64encode(image_file.read()).decode()
     [61](https://file+.vscode-resource.vscode-cdn.net/Users/ceyda.1/workspace/WORK/data-ml/title-attribute/notebooks/data/~/workspace/WORK/base_11/lib/python3.11/site-packages/argilla/_helpers/_media.py:61)         mimetype = f"image/{file_path.suffix[1:]}"

IsADirectoryError: [Errno 21] Is a directory: '.'

But now that I retried it, it was giving this error when image field was None. So I guess this just needs better error message or None handling when it is not a required field 👍