Allow error pages to use the default theme specified in cas.properties

[marwatk]

• Brief description of changes applied
• Test cases for all modified changes, where applicable
• The same pull request targeted at the master branch, if applicable
• Any documentation on how to configure, test
• Any possible limitations, side effects, etc
• Reference any other pull requests that might be related

This is the master branch version of #4962:

We noticed a bug that error pages (404, 500) wouldn't honor the default theme set in cas.properties. You can verify this by running a custom theme (even just a different CSS background color) and then trying to visit login2 instead of login.

This MR fixes that issue along with test cases to prove it. I'll follow up with a master version as well.

We also noticed that error page handling falls through to SpringTemplateResolver instead of using ChainingTemplateViewResolver which then caches the resulting view. This prevents custom theme views from ever appearing again (specifically the header). I spent a little time trying to determine why only the error pages would exhibit that behavior but came up empty (though, admittedly I didn't spend a ton of time since we only use a simple theme and fixing the error page 'solves' it for us). Future work may want to investigate that behavior.

[codecov]

Codecov Report

Merging #4963 into master will decrease coverage by 37.20353%.
The diff coverage is 0.00000%.

@@                  Coverage Diff                  @@
##                master      #4963          +/-   ##
=====================================================
- Coverage     40.33519%   3.13166%   -37.20353%     
+ Complexity        7386        697        -6689     
=====================================================
  Files             2410       2410                  
  Lines            55371      55370           -1     
  Branches          4544       4544                  
=====================================================
- Hits             22334       1734       -20600     
- Misses           31475      53473       +21998     
+ Partials          1562        163        -1399     

Flag	Coverage Δ	Complexity Δ
#actuator	?	?
#attributes	?	?
#audit	?	?
#cas	?	?
#cas-config	?	?
#cassandra	?	?
#cosmosdb	0.04334% <0.00000%> (ø)	10.00000 <0.00000> (ø)
#couchbase	?	?
#ehcache	?	?
#expiration-policy	?	?
#hazelcast	?	?
#ignite	2.99440% <0.00000%> (+0.00006%)	660.00000 <0.00000> (ø)
#infinispan	2.77407% <0.00000%> (-0.01439%)	639.00000 <0.00000> (-4.00000)
#influxdb	?	?
#jms	?	?
#jmx	?	?
#kafka	?	?
#logout	?	?
#mail	?	?
#mariadb	?	?
#memcached	?	?
#metrics	?	?
#mssql	?	?
#oauth	?	?
#oidc	?	?
#oracle	0.00722% <0.00000%> (ø)	1.00000 <0.00000> (ø)
#password-ops	?	?
#radius	?	?
#services	?	?
#shell	?	?
#sms	?	?
#spnego	?	?
#tickets	?	?
#uma	?	?
#util	?	?
#web	?	?
#zookeeper	?	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ	Complexity Δ
...cas/web/view/ThemeClassLoaderTemplateResolver.java	0.00000% <0.00000%> (-70.58823%)	0.00000 <0.00000> (-4.00000)
...apereo/cas/web/view/ThemeFileTemplateResolver.java	0.00000% <0.00000%> (-73.33333%)	0.00000 <0.00000> (-4.00000)
...i/src/main/java/org/apereo/cas/util/JsonUtils.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-4.00000%)
.../src/main/java/org/apereo/cas/util/RegexUtils.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-13.00000%)
...rc/main/java/org/apereo/cas/util/LoggingUtils.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-4.00000%)
...ain/java/org/apereo/cas/util/http/HttpMessage.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-4.00000%)
...in/java/org/apereo/cas/audit/AuditableContext.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-10.00000%)
.../java/org/apereo/cas/web/view/DynamicHtmlView.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-2.00000%)
...n/java/org/apereo/cas/ticket/ExpirationPolicy.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-1.00000%)
...n/java/org/apereo/cas/ticket/TicketDefinition.java	0.00000% <0.00000%> (-100.00000%)	0.00000% <0.00000%> (-1.00000%)
... and 1289 more

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