PDFCLOUD-2509 Add JSON Payload Java samples

[datalogics-tsmith]

Continuing from #62 to add more samples

[datalogics-kam]

The new JSON Payload directory needs a pom.xml; you can probably copy it from the Multipart Payload directory without changes; most likely it'll work since Maven POMs use configuration-by-convention; it'll just find your sources.

My bad, I didn't see it in the GitHub file list, but it was there in the checkout.

Then, the GitHub Action to run mvn verify needs another step here...just run mvn with the new directory as well. To make it easy to see in the logs, make it another step, like:

diff --git a/.github/workflows/verify-java.yml b/.github/workflows/verify-java.yml
index 80e53d5..bc53ada 100644
--- a/.github/workflows/verify-java.yml
+++ b/.github/workflows/verify-java.yml
@@ -23,5 +23,7 @@ jobs:
             # The "Build with Maven" step runs the Maven `verify` target in non-interactive mode to ensure that your
             # code builds, tests pass, and a package can be created.
             # The -f option indicates the root of the Maven project, where the pom.xml is located
-            -   name: Build with Maven
+            -   name: Build Multipart Payload examples with Maven
                 run: mvn -f 'Java/Endpoint Examples/Multipart Payload' --show-version --batch-mode --update-snapshots verify
+            -   name: Build JSON Payload examples with Maven
+                run: mvn -f 'Java/Endpoint Examples/JSON Payload' --show-version --batch-mode --update-snapshots verify

That'll make sure the code is checked in CI.

[datalogics-cgreen]

Will merge this PR to get both sets of single calls in.

EDIT: My mistake – that's not quite what happened, but the merge is still good.