* Move from env variables to SiteConfig
Related to #5384
This PR only deals with the first remaining part outlined in the issue, starting to use existing SiteConfig keys instead of the env variables.
* Restore Envfile to original version for now
* Add ApiSecret model scaffold
* Add relationships between ApiSecret, User, Organization
* Add placeholder template to account tab
* Add description column to ApiSecrets
* Add very basic access token generation
* Add basic access token deletion
* Show access token on success flash
* Add placeholder message when user has no secrets
* Use cta style on token generation button
* Add presence validation for ApiSecret description
* Add ApiSecrets factory
* Add pundit policy for ApiSecret
* Nest form field within api_secret hash to allow rails strong params
* Use pundit to authorize ApiSecretController actions
* Add error message flash for ApiSecretsController actions
* Add specs for ApiSecretsController
* Add length validation to api secret description
* Flash model error instead of generic message on save failure
* Truncate ApiSecret factory objects descriptions to prevent validation error
* Remove length restriction on ApiSecret.description
* Use darker font color for token creation date
* Consolidate ApiSecret migrations