feat: Use UploadHandler in documentation

[caalador]

fixes #4304

[github-actions]

AI Language Review

In the Java files:

1. UploadAllFiles.java:

   • The line InMemoryUploadHandler inMemoryHandler = UploadHandler.inMemory((metadata, data) -> {}); initializes a handler but does not use or demonstrate processing of the uploaded files within the lambda. Consider providing a basic implementation or comment placeholder indicating intended use.

2. UploadAutoUploadDisabled.java:

   • Similar to UploadAllFiles.java, the inMemoryHandler is initialized but not used within the lambda for file processing. Adding at least a comment to guide users on how to handle the uploaded data would be helpful.

3. UploadBasic.java:

   • The InMemoryUploadHandler implementation includes a comment // processFile(data, fileName); which is a useful placeholder, but this should be consistent across examples in other files for clarity.

4. UploadDragAndDrop.java:

   • InMemoryUploadHandler instances are initialized with empty lambdas, similar to the other files. Providing a comment or simple usage example might improve clarity regarding handling uploads.

5. UploadDropLabel.java:

   • The handler is again initialized with an empty lambda. Consider providing a comment or basic example of handling the uploaded content for clarity.

6. UploadFileBuffer.java:

   • The addition of FileUploadHandler is clear, but ensuring consistency with comments or usage examples across files would enhance overall documentation and usability for those unfamiliar with the pattern.

In the AsciiDoc files:

1. File Handling:

   • In the section describing InMemoryUploadHandler, consider adding a step or explanation about potential memory limitations or best usage practices, as in-memory storage could lead to issues with large files.
   • Similarly, for the FileUploadHandler description, it may be beneficial to add a note or best practice regarding file storage paths and permissions.

2. Using UploadHandler to Receive an Incoming Data Stream:

   • Provide an explanation for where in the application lifecycle or architecture the registration of the UploadHandler should typically occur, as this could guide users in correctly integrating it into their projects.
   • Including a precaution about handling multiple files separately, especially if each triggers a separate invocation of handleUploadRequest, could prevent potential misunderstandings.

Overall, ensure consistent use of comments or placeholders in code examples to demonstrate handling of uploaded data, as this enhances comprehension for users not familiar with the API or design patterns.