validation: register validation blueprint

[vgranata]

Register validation blueprint.

When a project is submitted a validation email is sent to reviewers. The body of the email is a template defined in the validation module. To make the template reachable the blueprint 'validation' needs to be registered.

Closes https://github.com/rero/sonar/issues/858 Co-Authored-by: Valeria Granata valeria@chaw.com

Why are you opening this PR?

issue https://github.com/rero/sonar/issues/858

Code review check list

• [ ] Commit message template compliance.
• [ ] Commit message without typos.
• [ ] File names.
• [ ] Functions names.
• [ ] Functions docstrings.
• [ ] Unnecessary commited files?
• [ ] Extracted translations?

[jma]

Can you give more details in your commit message. I do not understand the purpose of this PR.

[PascalRepond]

@vgranata Please rebase, fix conflicts and merge.