In records the IDs like the realm_id and user_profile_id
of 'records.json' should be integers. This was missing in the
S3 backend and this commit fixes that.
Added tests for this as well.
For the emojis, In 'records.json', the record should contain
the attribute 'file_name', which was missing in the S3 backend.
This commit adds this attribute, as well as tests for the
records of uploads, avatars and emojis in both local and S3 backend.
