- make derivatives a named route for url helpers

it's not handled correctly, and sometimes passed directly to the underlying
process (e.g., shrine)

- restore file_identifier set

don't try to infer the id of the file metadata node. these resources are handled
differently by different adapters, just making one with a file_identifer set
doesn't do the trick.

see, e.g., the usage here:
https://github.com/samvera/hyrax/blob/main/spec/models/hyrax/file_metadata_spec.rb#L27-L43

all but one of the arguments to `ValkyrieUpload` are arguments to a specific
action (an upload), but the `storage_adapter` parameter is more stable and
cumbersome to pass per upload.

in the default case, this doesn't much matter, but when using one of the
alternative adapters (e.g. for derivatives), we can reduce the dependencies for
collaborator objects by allowing them to use a preconfigured instance of the
upload service. e.g:

```ruby
derivatives_uploader.upload(filename: 'test.txt', file_set: my_fs, io: StringIO.new('test'))
```

instead of:

```ruby
derivatives_adapter = Hyrax.config.derivatives_storage_adapter
Hyrax::ValkyrieUpload.file(filename: 'test.txt', file_set: my_fs, io: StringIO.new('test'))
```

Previously the final group of characters was not included in the extracted id.

Attempting to resave a converted resource resulted in an error due to the attribute setter now being defined by ActiveFedora instead of ActiveTriples.

…ot itself

Add mock ids to satisfy services that need ids.
Include mock_thumbnail in file_ids
thumbnail_path should include the fileset id