Fix: Handle binary file uploads on Plain Text pages correctly

[srikaaviya]

Previously, uploading a binary file (e.g., .pages, .pdf) to replace a Text page caused a 'UnicodeDecodeError or data validation error' because the system attempted to decode the binary content as text based on the existing page type.
This commit:

1. Checks if the uploaded file is binary based on .
2. Skips text decoding for binary files.
3. Updates the item's contenttype metadata to match the uploaded file, ensuring subsequent validation passes.

[UlrichB22]

@srikaaviya, did you install the pre-commit hooks in your development environment as described in
https://moin-20.readthedocs.io/en/latest/devel/development.html#install-pre-commit-hooks ?

[roland-ruedenauer]

I'm not quite sure if it is a good idea to be able to switch from "text" content to binary content. One immediate problem this will trigger is how diffs between item revisions behave.

Does Moin2 even support switching markup type from e.g. markdown to rST?

[UlrichB22]

Does Moin2 even support switching markup type from e.g. markdown to rST?

Yes, there is a Convert action in the items view.

[srikaaviya]

@srikaaviya, did you install the pre-commit hooks in your development environment as described in https://moin-20.readthedocs.io/en/latest/devel/development.html#install-pre-commit-hooks ?

Yes, I installed and ran the pre-commit hooks.

[srikaaviya]

I'm not quite sure if it is a good idea to be able to switch from "text" content to binary content. One immediate problem this will trigger is how diffs between item revisions behave.

Does Moin2 even support switching markup type from e.g. markdown to rST?

Yes, switching content types will cause the Diff view to crash. However, I can implement a safety check to fix this: if the content types are different, the Diff view will simply show a message saying they cannot be compared, instead of error. Will it work?

[UlrichB22]

Yes, please add the check to avoid tracebacks.
It would be nice if you can squash the first commits.