Add configurable privacy statement link

[lampajr]

Fixes Issue

Fixes #1408

Changes proposed

Provide additional privacy statement in the About popup:

The link/URL is configurable at installation/build level using property horreum.privacy.

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• My change requires changes to the documentation.
• I have updated the documentation accordingly.
• All new and existing tests passed.

[lampajr]

There are still a couple of open points:

• Set a reasonable default value, right now I am using /link/to/privacy/statement. Any suggestion?
• Is Privacy category name fine on UI?

I kept the new VersionInfo.privacyStatement field optional from OpenAPI perspective in order to be backward compatible, the webapp should manage when the field is undefined.

[johnaohara]

Please can you rebase

[johnaohara]

There are still a couple of open points:

* [ ]  Set a reasonable default value, right now I am using `/link/to/privacy/statement`. Any suggestion?

I am not sure if there is a reasonable default, it is probably best to leave this either commented out in application.properties and not display anything by default. Users can see that it is an option that can be set and/or we need an admin guide that covers the setting

* [ ]  Is `Privacy` category name fine on UI?

I kept the new VersionInfo.privacyStatement field optional from OpenAPI perspective in order to be backward compatible, the webapp should manage when the field is undefined.

I think it is fine to be a configuration option for Horreum as it should apply system wide to all users of the installation

[johnaohara]

merged, thank you for your contribution!

[lampajr]

@johnaohara do we want to address #1437 (comment) in a separate PR? because otherwise by default the webpage will show /link/to/privacy/statement as privacy statement which does not make sense

[johnaohara]

@johnaohara do we want to address #1437 (comment) in a separate PR? because otherwise by default the webpage will show /link/to/privacy/statement as privacy statement which does not make sense

yes please, i have already merged this PR