Allow a default space to be specified for a template provider, which will automatically create the document in that space

We should devise a mechanism for the template providers which would allow to force the creation of a document in a specific space, and display the template in all creation forms, not only in the spaces where the provider is available.

Nowadays we have a list of available spaces and, when creating a page, the template provider is shown in the create form only if the context is one of those available spaces.
In addition, if the template provider is available in only one space, the user still gets an input with the space input allowing him to fill in a space, but actually accepting only one value.

What would be interesting as a use case is to be able to choose, for example, the blog post template from everywhere in the wiki (e.g. on the main page) and the page you create would be filled in automatically in the Blog space (or whatever space is defined as a default space for that provider).
This can be interesting to combine with the applications created with app within minutes, which could all "plug" their templates in the create form, and allow a user to create an entry from everywhere in the wiki, using the universal create button in the top page menu.

Basically this would help viewing the create button as an universal create button to create content on the wiki (not in the current space), where the wiki is seen as a collection of applications.

The one or the other behaviour could be switched with a configuration parameter, since I think they refer 2 types of usages for the wiki.