[ACA-1957] Library metadata - check title uniqueness

[pionnegru]

PR Checklist

Please check if your PR fulfills the following requirements:

- [ ] The commit message follows our guidelines: https://github.com/Alfresco/alfresco-content-app/blob/master/CONTRIBUTING.md#commit
- [ ] Tests for the changes have been added (for bug fixes / features)
- [ ] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Application / Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[ ] No

Other information

[codecov-io]

Codecov Report

Merging #767 into development will increase coverage by 0.21%.
The diff coverage is 94.11%.

@@              Coverage Diff               @@
##           development    #767      +/-   ##
==============================================
+ Coverage        51.09%   51.3%   +0.21%     
==============================================
  Files              106     106              
  Lines             2965    2980      +15     
  Branches           593     595       +2     
==============================================
+ Hits              1515    1529      +14     
- Misses            1372    1373       +1     
  Partials            78      78

Impacted Files	Coverage Δ
...ry-metadata-tab/library-metadata-form.component.ts	93.93% <94.11%> (-0.51%)	⬇️

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