Merge branch 'development' of https://gitlab.cs.ut.ee/agile-software-development/volt into development

# Conflicts:
#   ci/deploy.yml

Merge branch 'development' of https://gitlab.cs.ut.ee/agile-software-development/volt into development

Deploy application to Gigalixir

See merge request !51

[#194]: improve value readability

See merge request !50

Resolve "Customer deletes orders with discount"

See merge request !48

[#29]: Courier sees orders and can go on and off duty

See merge request !46

[#51]: customer order history

See merge request !47

[#47,#80,#81,#78]: restaurant see order history / Discount

See merge request !43

Update README.md

See merge request !45

Resolve "US-43: Customer should see what restaurants are closed"

See merge request !44