FIX - Keycloak server execution failing at startup

[Agnul97]

The startup of the keycloak server inside the kapua/kapua-keycloak image was failing due to missing of some parameters in the startup script. Basically, the server was started in production mode but this mode requires additional configurations of some aspects, as stated here https://www.keycloak.org/server/configuration-production, that was missing.

With this PR, I inserted the missing configuration parameters. In this way, with the kapua/kapua-keycloak image (so, with the --sso option on the deploy) we propose a demo image to test the sso feature. Finally, I updated the documentation, particularly in the part were it is explained how to run a stand-alone keycloak image for the case of a (real) production mode deployment.

Specifically, I worked on these aspects

1. Inserted missing cli parameters to fix the server startup issue and provide an HTTP deployment
2. Fixed the way SSL certificates were imported with the volumes setting in the compose files: this was bugged for a typo in the path and certs were not imported at all
3. Used certs at point 1. to provide the capability of an HTTP + SSL deployment, with a dedicated env. variable to enable/disable SSL if needed (KEYCLOAK_SSL_ENABLE, like done in the console with KAPUA_SSL_ENABLE) and automatically set via the --ssl option with the deployment script
4. Updated the developer guide in the SSO section: this was not updated after the bump to the image version 21.1 (from the jboss 7 version) and I've fixed the gap, also I touched other aspects that were wrong
5. Updated the README.md file inside the assembly folder: I noticed that there was a lot of redundant content with respect to the developer guide, so I inserted some references to that guide in order to solve the redundancy

[codecov]

Codecov Report

Merging #3894 (79dfd2b) into develop (e1a0e7d) will decrease coverage by 0.02%.
Report is 10 commits behind head on develop.
The diff coverage is 10.94%.

❗ Current head 79dfd2b differs from pull request most recent head 2369c4a. Consider uploading reports for the commit 2369c4a to get more accurate results

@@              Coverage Diff              @@
##             develop    #3894      +/-   ##
=============================================
- Coverage      20.54%   20.52%   -0.02%     
  Complexity         6        6              
=============================================
  Files           1940     1944       +4     
  Lines          41547    41649     +102     
  Branches        3940     3946       +6     
=============================================
+ Hits            8534     8549      +15     
- Misses         32616    32703      +87     
  Partials         397      397              

Files	Coverage Δ
.../eclipse/kapua/app/api/core/model/CountResult.java	100.00% <ø> (ø)
...eclipse/kapua/app/api/web/JaxbContextResolver.java	77.77% <ø> (ø)
...ice/authentication/DeviceAuthenticationModule.java	100.00% <100.00%> (ø)
...evice/registry/KapuaDeviceRegistrySettingKeys.java	100.00% <100.00%> (ø)
...e/device/registry/connection/DeviceConnection.java	0.00% <ø> (ø)
...stry/connection/option/DeviceConnectionOption.java	0.00% <ø> (ø)
.../service/device/registry/DeviceRegistryModule.java	80.00% <100.00%> (-0.65%)	⬇️
.../eclipse/kapua/locator/guice/GuiceLocatorImpl.java	69.53% <0.00%> (-0.55%)	⬇️
.../api/resources/v1/resources/DeviceConnections.java	0.00% <0.00%> (ø)
...ion/UserPassDeviceConnectionCredentialAdapter.java	50.00% <50.00%> (ø)
... and 11 more

... and 1 file with indirect coverage changes

[Coduz]

First, I want to suggest to switch to KEYCLOAK_SSL_ENABLE instead of KEYCLOAK_DISABLE_SSL which enables SSL when is false and disable SSL true. We can talk about this, if there is any doubt on this point

Second, it would be possible to have the Keycloak SSL enabled based on the --ssl option available in the Docker Compose deployment? "One SSL option to rule them all" it is easier to use.

Please also remove KEYCLOAK_* env defined in deployment/docker/compose/docker-compose.yml for the kapua-console component.

[Coduz]

Please don't use this reverse logic ENV to enable component.

It is far easier to understand KEYCLOAK_SSL_ENABLE when is defined and used.
The default can be false to indicate that a feature is disabled by default.