Add Upgrade-Guide and Learn section to docs

[mdapena]

Initial Checks

• The code compiles successfully without any errors or warnings.
• I have personally tested these changes on my local environment.
• I have ensured that relevant documentation has been added or updated.
• I adhere to the project structure and code standards defined in the documentation.
• My code follows the established coding style guidelines.
• I have added tests for the new code (if applicable).
• All existing tests have passed successfully.

Description

This pull request introduces an Upgrade-Guide section to the Pyventus documentation for the v0.7 release, refines the security policy for improved clarity, and replaces the existing tutorials section with a new Learn section to encompass a broader range of educational resources.