Investigate whether we can capture a photo from the camera without storing it on disk
When sending an ACTION_IMAGE_CAPTURE intent it's possible to pass a content URI that represents a file where the camera app should store the image. (On Android 7+ the URI has to be obtained from a FileProvider.) In itself that's not much use - it would allow us to specify a file in Briar's private data dir, which is better than using the shared media dir, but the file would still be unencrypted.
Investigate whether it's possible to pass a URI that represents a pipe rather than an ordinary file, in which case we could read the data from the pipe into the encrypted db (or an encrypted temporary file).