[rest_api] exposed 3 get functions
[rest_api] exposed 3 get functions

 - get_volume
 - get_attachment
 - get_attachments

ael-code/libreant,leophys/libreant,insomnia-lab/libreant,ael-code/libreant,leophys/libreant,insomnia-lab/libreant,leophys/libreant,ael-code/libreant,ael-code/libreant,insomnia-lab/libreant,insomnia-lab/libreant,leophys/libreant