[GWC-1171] Improve handling special characters in the GWC Demos Page

[sikeoka]

#1171
This PR updates the GWC Demos Page to properly escape special characters from GeoServer catalog information. One thing to note here is that StringEscapeUtils::escapeEcmaScript is not secure when used in HTML attributes so the OWASP Encoder library is used instead.

[aaime]

Looks overall good, one QA failure.

[aaime]

Causes QA failure:

06:26:04,481 [INFO] PMD Failure: org.geowebcache.demo.Demo:103 Rule:AvoidPrintStackTrace Priority:3 Avoid printStackTrace(); use a logger call instead..
06:26:04,485 [INFO] PMD Failure: org.geowebcache.demo.Demo:103 Rule:AvoidPrintStackTrace Priority:3 Avoid printStackTrace(); use a logger call instead..

[sikeoka]

Fixed.

[sikeoka]

There was a Java heap space error in the downstream build.

[aaime]

The backport to 1.23.x failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply 49b26ff7... [GWC-1171] Improve handling special characters in the GWC Demos Page
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

stdout

Auto-merging geowebcache/core/src/main/java/org/geowebcache/demo/Demo.java
CONFLICT (content): Merge conflict in geowebcache/core/src/main/java/org/geowebcache/demo/Demo.java

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.23.x 1.23.x
# Navigate to the new working tree
cd .worktrees/backport-1.23.x
# Create a new branch
git switch --create backport-1173-to-1.23.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 49b26ff7b0b49113d1e0ed3f45ffc52b094934eb
# Push it to GitHub
git push --set-upstream origin backport-1173-to-1.23.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.23.x

Then, create a pull request where the base branch is 1.23.x and the compare/head branch is backport-1173-to-1.23.x.