Previous code assumed server responses would always be JSON, and had no
special handling for mis-configured servers that sometimes return HTML;
for example, if the server has a bug, or there's a reverse proxy in
front of the server issuing DoS-prevention challenges.
This could cause errors to show with no useful debugging information.
Update `ApiResult` to check the content-type in the response and return
one of two new errors if the content-type is missing or wrong. Also
include the HTTP code in `ApiResponse` for use elsewhere.
Update `ThrowableExtensions` to pull the `error` and optional
`description` out of the error body.
Update `PachliError` so `formatArgs` can be an array of arbitrary types,
not just strings.
Update `MediaUploader`; expose the different errors as new
`MediaUploaderError` types instead of `Exception` subclasses, and return
`Result<V, E>` where appropriate.
Update `ComposeViewModel` to use the new `MediaUploaderError` types and
create new `PickMediaError` to report issues there, replacing
`VideoOrImageException`.
Update `ComposeActivity` to use the new error types and show errors
until the user dismisses them, so they're better able to see and report
problems.
Fixes#704.
5aacb02ea0