REST API default user is not created

**Describe the bug**
When I launch the `flowable/all-in-one` Docker image the REST API default user is not created:


**Expected behavior**
That the REST API default user is created and is granted the `access-rest-api` privilege:


**Code**
For example:

```
docker run -d --name flowable \
-p 8080:8080 \
-e FLOWABLE_REST_APP_ADMIN_USER_ID='flowable-rest' \
-e FLOWABLE_REST_APP_ADMIN_PASSWORD='test' \
-e FLOWABLE_REST_APP_ADMIN_FIRST_NAME='Flowable Rest API' \
-e FLOWABLE_REST_APP_ADMIN_LAST_NAME='Administrator' \
--env-file ./no-ldap-env.txt \
flowable/all-in-one
```

Check the env variables are set correctly:

```
docker inspect -f \
'{{range $index, $value := .Config.Env}}{{println $value}}{{end}}' \
flowable | grep FLOW
```

Output:

```
FLOWABLE_IDM_APP_ADMIN_USER_ID=flowable
FLOWABLE_IDM_APP_ADMIN_PASSWORD=test
FLOWABLE_IDM_APP_ADMIN_FIRST_NAME=Flowable
FLOWABLE_IDM_APP_ADMIN_LAST_NAME=Administrator
FLOWABLE_IDM_APP_ADMIN_EMAIL=admin@flowable.org
FLOWABLE_COMMON_APP_IDM_ADMIN_USER=flowable
FLOWABLE_COMMON_APP_IDM_ADMIN_PASSWORD=test
FLOWABLE_REST_APP_ADMIN_LAST_NAME=Administrator
FLOWABLE_REST_APP_ADMIN_USER_ID=flowable-rest
FLOWABLE_REST_APP_ADMIN_PASSWORD=test
FLOWABLE_REST_APP_ADMIN_FIRST_NAME=Flowable Rest API
```

no-ldap-env.txt :

```
#
# Relaxed Binding (Externalised Configuration)
#
# Property Note
# acme.my-project.person.first-name Kebab case, which is recommended for use in .properties and .yml files.
# acme.myProject.person.firstName Standard camel case syntax.
# acme.my_project.person.first_name Underscore notation, which is an alternative format for use in .properties and .yml files.
# ACME_MYPROJECT_PERSON_FIRSTNAME Upper case format, which is recommended when using system environment variables.
#
# See: https://docs.spring.io/spring-boot/docs/2.0.7.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-relaxed-binding

# Ref: https://docs.spring.io/spring-boot/docs/current/reference/html/appendix-application-properties.html
# Ref: https://github.com/flowable/flowable-engine/blob/master/modules/flowable-app-rest/src/main/resources/flowable-default.properties
# Ref: https://github.com/flowable/flowable-engine/blob/master/modules/flowable-ui-idm/flowable-ui-idm-app/src/main/resources/flowable-default.properties
# Ref: https://flowable.com/open-source/docs/bpmn/ch15-REST/

# Note: UPPER_CASE_FORMAT is recommended when using system environment variables.

#
# DEFAULT ADMINISTRATOR ACCOUNTS
#

FLOWABLE_IDM_APP_ADMIN_USER_ID=flowable
FLOWABLE_IDM_APP_ADMIN_PASSWORD=test
FLOWABLE_IDM_APP_ADMIN_FIRST_NAME=Flowable
FLOWABLE_IDM_APP_ADMIN_LAST_NAME=Administrator
FLOWABLE_IDM_APP_ADMIN_EMAIL=admin@flowable.org

FLOWABLE_COMMON_APP_IDM_ADMIN_USER=flowable
FLOWABLE_COMMON_APP_IDM_ADMIN_PASSWORD=test

#
# DEFAULT REST API ACCOUNTS - See: https://flowable.com/open-source/docs/bpmn/ch15-REST/
#

# flowable.rest.app.admin.user-id=rest-admin
# flowable.rest.app.admin.password=test
# flowable.rest.app.admin.first-name=Rest
# flowable.rest.app.admin.last-name=Admin

#
# DEFAULT REST API ACCOUNTS - See: https://github.com/flowable/flowable-engine/blob/master/modules/flowable-app-rest/src/main/resources/flowable-default.properties
#

# flowable.rest.app.admin.user-id=rest-admin
# flowable.rest.app.admin.password=test
# flowable.rest.app.admin.firstname=Rest
# flowable.rest.app.admin.lastname=Admin

#
# DEFAULT REST API ACCOUNTS
#

# FLOWABLE_REST_APP_ADMIN_USERID=flowable-rest
# FLOWABLE_REST_APP_ADMIN_PASSWORD=test
# FLOWABLE_REST_APP_ADMIN_FIRSTNAME=Flowable Rest API
# FLOWABLE_REST_APP_ADMIN_LASTNAME=Administrator

# FLOWABLE_REST_APP_ADMIN_USER_ID=flowable-rest
# FLOWABLE_REST_APP_ADMIN_PASSWORD=test
# FLOWABLE_REST_APP_ADMIN_FIRST_NAME=Flowable Rest API
# FLOWABLE_REST_APP_ADMIN_LAST_NAME=Administrator

# https://unix.stackexchange.com/questions/23659/can-shell-variable-name-include-a-hyphen-or-dash
# https://github.com/gliderlabs/docker-alpine/issues/290

#
# MISC
#

# https://github.com/flowable/flowable-engine/issues/1958#issuecomment-571569786
# -e "spring.datasource.url=jdbc:h2:~/flowable-db/db;AUTO_SERVER=TRUE;AUTO_SERVER_PORT=9091;DB_CLOSE_DELAY=-1"

# SPRING_DATASOURCE_URL=jdbc:h2:~/flowable-db/db
# AUTO_SERVER=TRUE
# AUTO_SERVER_PORT=9091
# DB_CLOSE_DELAY=-1

# HTTP Status 404 – Not Found
# Type Status Report
#
# Message /flowable-idm
#
# Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.
#
# Apache Tomcat/9.0.14
```

**Additional context**

As per the Spring Boot Relaxed Binding [documentation](https://docs.spring.io/spring-boot/docs/2.0.7.RELEASE/reference/html/boot-features-external-config.html#boot-features-external-config-relaxed-binding), UPPER_CASE_FORMAT is used when using system environment variables.

**Note:** Unix shells cannot include a hyphen in a variable name.

Interesting (may be related) when I tried to set the [spring.datasource.url](https://github.com/flowable/flowable-engine/issues/1958#issuecomment-571569786) in the --env-file file I received the following error:

```
HTTP Status 404 – Not Found
Type Status Report

Message /flowable-idm

Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.

Apache Tomcat/9.0.14
```

See: [Serendipity CEP - Developer Documentation](https://github.com/Robinyo/serendipity/blob/master/docs/developer.md)