[Fixes #6899] Customize metadata template

[mattiagiupponi]

With this PR I want to externalize the catalog metadata template through a settings variable in order to make it easier to configure the template for the metadata

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[gannebamm]

I am aware that this PR is a draft. To get merged it will need some more steps like:

• The PR has a wrong label
• Could you please provide an issue with the label feature for this PR?
• The documentation should show how those templates has to be generated and modified
• tests?

[codecov]

Codecov Report

Merging #6894 (afcade8) into master (82c8602) will increase coverage by 29.22%.
The diff coverage is 49.00%.

@@             Coverage Diff             @@
##           master    #6894       +/-   ##
===========================================
+ Coverage   22.89%   52.12%   +29.22%     
===========================================
  Files         573      573               
  Lines       40900    40961       +61     
  Branches     5500     5505        +5     
===========================================
+ Hits         9364    21349    +11985     
+ Misses      31203    18268    -12935     
- Partials      333     1344     +1011     

[mattiagiupponi]

Hi @gannebamm
Thanks for the comment, I fixed the points in your comment.
Here is the link to the PR for update the documentation.
Any other comment is appreciated