SSO - OIDC environment variables renaming

[gbarbon]

This PR renames the environment variables used for OIDC (OpenID Connect) by introducing the KAPUA_OPEID_ prefix.
Moreover, all the SSO OIDC documentation has been updated accordingly and improved (with a focus on environment variables).

Related Issue
Fix #3261

Description of the solution adopted
n/a

Screenshots
n/a

Any side note on the changes made
Please note that this is a breaking change , since the renaming of the environment variable names in an existing environment will prevent Kapua from loading the SSO provider configuration, if existing environment variables are not updated accordingly.

[codecov]

Codecov Report

Merging #3298 (e990e3a) into develop (5b1deb8) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##             develop    #3298      +/-   ##
=============================================
- Coverage      55.03%   54.97%   -0.06%     
+ Complexity       787      786       -1     
=============================================
  Files           1478     1478              
  Lines          30235    30235              
  Branches        2523     2523              
=============================================
- Hits           16639    16622      -17     
- Misses         12682    12691       +9     
- Partials         914      922       +8     

Impacted Files	Coverage Δ	Complexity Δ
...pua/job/engine/exception/JobResumingException.java	0.00% <0.00%> (-25.00%)	0.00% <0.00%> (ø%)
...kapua/job/engine/exception/JobEngineException.java	54.54% <0.00%> (-9.10%)	0.00% <0.00%> (ø%)
.../DeviceManagementOperationRegistryServiceImpl.java	66.07% <0.00%> (-7.15%)	0.00% <0.00%> (ø%)
...ua/broker/core/listener/DeviceMessageListener.java	60.46% <0.00%> (-6.98%)	0.00% <0.00%> (ø%)
...ce/management/commons/call/DeviceCallExecutor.java	62.79% <0.00%> (-4.66%)	0.00% <0.00%> (ø%)
...e/registry/internal/DeviceRegistryServiceImpl.java	59.15% <0.00%> (-2.82%)	0.00% <0.00%> (ø%)
...atch/persistence/jpa/JpaExecutionInstanceData.java	87.80% <0.00%> (-2.44%)	22.00% <0.00%> (-1.00%)
...apua/job/engine/jbatch/JobEngineServiceJbatch.java	45.00% <0.00%> (-1.67%)	8.00% <0.00%> (ø%)
.../jbatch/persistence/JPAPersistenceManagerImpl.java	30.56% <0.00%> (-1.04%)	30.00% <0.00%> (ø%)
...pse/kapua/commons/service/internal/ServiceDAO.java	75.23% <0.00%> (-0.95%)	0.00% <0.00%> (ø%)
... and 1 more