Add guidance on using O_DIRECT option to bypass Mountpoint's caches

Signed-off-by: Daniel Carl Jones <[email protected]>

doc/CONFIGURATION.md

@@ -243,6 +243,9 @@ Mountpoint caching can be further configured,
 such as adjusting the metadata time-to-live (TTL) or the maximum space allowed to be used by the data cache.
 Review the caching options available using `mount-s3 --help`.
 
+To avoid using the cache, an application can use the `O_DIRECT` option (or language equivalent) when opening a file for reading.
+When this option is provided, Mountpoint will check for the latest object in S3 and read object content from S3 rather than cached data.
+
 > [!WARNING]
 > Caching relaxes the strong read-after-write consistency offered by Amazon S3 and Mountpoint in its default configuration.
 > See the [consistency and concurrency section of the semantics documentaton](./SEMANTICS.md#consistency-and-concurrency) for more details.