[Validator] fixed Boolean handling in XML constraint mappings (closes #5603)
merged branch fabpot/validator-xml-loader (PR #8831)

This PR was merged into the 2.2 branch.

Discussion
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[Validator] fixed Boolean handling in XML constraint mappings

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #5603
| License       | MIT
| Doc PR        | n/a

ping @bschussek

Commits
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33b0a17 [Validator] fixed Boolean handling in XML constraint mappings (closes #5603)