Documentation updates for backend

[danielnaab]

Adds ADRs for #247:

• Database strategy
• Authentication
• REST api

[github-actions]

Terraform plan for tts-10x-atj-dev

Plan: 0 to add, 2 to change, 0 to destroy.

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
!~  update in-place

Terraform will perform the following actions:

  # cloudfoundry_app.tts-10x-atj-dev-server-doj_tts-10x-atj-dev-server-doj-app_380DB029 will be updated in-place
!~  resource "cloudfoundry_app" "tts-10x-atj-dev-server-doj_tts-10x-atj-dev-server-doj-app_380DB029" {
!~      docker_image                    = "ghcr.io/gsa-tts/atj-platform/server-doj:6b53414977959c950ea050e095929a5f34a12ac7" -> "ghcr.io/gsa-tts/atj-platform/server-doj:49a59aa007a4a646b212083bf16c761057fad2cb"
        id                              = "6246c063-6cf4-423d-812a-4bfdeb62bcae"
        name                            = "tts-10x-atj-dev-server-doj-app"
#        (17 unchanged attributes hidden)

#        (3 unchanged blocks hidden)
    }

  # cloudfoundry_app.tts-10x-atj-dev-server-kansas_tts-10x-atj-dev-server-kansas-app_337A9CF1 will be updated in-place
!~  resource "cloudfoundry_app" "tts-10x-atj-dev-server-kansas_tts-10x-atj-dev-server-kansas-app_337A9CF1" {
!~      docker_image                    = "ghcr.io/gsa-tts/atj-platform/server-kansas:6b53414977959c950ea050e095929a5f34a12ac7" -> "ghcr.io/gsa-tts/atj-platform/server-kansas:49a59aa007a4a646b212083bf16c761057fad2cb"
        id                              = "f7c60971-bffd-4a6e-a0bb-af1191079918"
        name                            = "tts-10x-atj-dev-server-kansas-app"
#        (17 unchanged attributes hidden)

#        (3 unchanged blocks hidden)
    }

Plan: 0 to add, 2 to change, 0 to destroy.

📝 Plan generated in Post Terraform plan to PR comment #295

[ethangardner]

Detailed and lightweight. Nice work.