- Clean up main.go (by moving init to init.go) and improve
composition comprehension.
- Refactor app context and init struct and field names.
- Update package dependencies in initialisation.
This commit introduces a `blobstore` package and refactors the existing
upload mechanism. Upload is now handled by `providers` and the two
bundled providers are `S3` and `Filesystem`. `app.Blobstore` initialises
the correct provider based on the configuration and handles `Put`,
`Delete` and `Get` operations.
- unchecked returns fixed (most)
- remove unused constants
- remove unsed structs
- function parameters unused or incorrectly used
- removed if else chains for error checks
- use regex MustCompile instead of compile
- spell checks
- preallocate slice cap when size known
- scope issues inside range
