Update 'Environment variables'

Environment-variables.md

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+# **DRAFT**
+## Configuration
+
+Application requires the following variables to be set. As an alternative to setting the environment variables, the respective lines in `application.properties` can be adjusted, or Java runtime parameters may be passed.
+
+
+* `CONTAINER_API`
+* `DB`
+* `DB_HOST`
+* `DB_SECRET`
+* `DB_USER`
+* `KC_HOST`
+* `KC_PORT`
+* `KC_REALM`
+* `KC_RESOURCE`
+* `LOGLEVEL`
+
+`LOGLEVEL` is optional and defaults to `INFO`. The other values are mandatory, the application will fail to operate without them.