feat(storage): add method to get file metadata

feat(storage): improve error handling in file download method

Adds function to generate signed URLs for uploading storage objects

Fixes issues with generating signed URLs for downloading objects

Functions for generating signed urls return errors instead of panicking on failure

Adds function for deleting a single object from storage

fix(auth): use correct struct for unmarshalling error response body

fix(auth): return ErrorResponse object as error to enable proper error handling

feat: add delete user function

Add admin get/create/update user (nedpals#35)

* Add admin get/create/update user

* Add admin generate link

Use postgrest-go v0.1.3 (nedpals#17)

Signed-off-by: Masudur Rahman <masudjuly02@gmail.com>

docs: update roadmap, usage

auth: access_token to authenticated details

improve response handling and skip body parsing if http status is 204

improve response handling and skip body parsing if http status is 204