Improve error logs for unsupported operations: File Overwrite, Random Write, Directory Shadowing, Unlink (without mount option)

[sauraank]

Description of change

Added clear message for the operations that are unsupported but did not had easy to understand logs. Added links to semantics for deletion and allowed filenames to be visible using Mountpoint. But, with links there is a risk that they can get broken once the content is moved somewhere else.
I will add another PR for troubleshooting page and down level the error noise to debug! in other Pull Requests.

With this new change, following are error logs that we receive:
For directory shadowing of file with same name, ls give following output -

WARN readdir{req=5 ino=1 fh=2 offset=17}: mountpoint_s3::inode::readdir::ordered: file 'out' (full key "out") is omitted because another directory 'out' exist with the same name.

For file deletion without using --allow-delete flag, give following in logs -

WARN unlink{req=8 parent=1 name="ini.txt"}: mountpoint_s3::fuse: unlink failed: Deletes are disabled. Use '--allow-delete' mount option to enable it.

Out of Write gives -

WARN write{req=52 ino=49 fh=3 offset=512 length=512 name="new.txt"}: mountpoint_s3::fuse: write failed: upload error: out of order write NOT supported by Mountpoint, aborting the upload; expected offset 0 but got 512

UPDATE: Overwriting a file is now supported, so the error message is the one set in PR #487 -

WARN file overwrite is disabled by default, you need to remount with --allow-overwrite flag and open the file in truncate mode (O_TRUNC) to overwrite it

Also changed the logging in case of finish writing to update status of Inode, but the Inode WriteStatus is in Invalid state. Earlier it was InodeNotWritable which is same error for File Overwrite when its flag is not enabled. Also, it did not completely explained that WriteStatus of the Inode is not valid for writing.

Relevant issues:
#533

Does this change impact existing behavior?

No. It only improves the error logging as mentioned above.

No, there is no breaking change.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and I agree to the terms of the Developer Certificate of Origin (DCO).

[monthonk]

@sauraank thanks for improving the logs! I have put a few comments.

[passaro]

Rather than adding a message here, I'd prefer having a specific InodeError case for each situation.

[monthonk]

LGTM