Handle collisions with existing spaces when importing Confluence spaces

If a Confluence package is imported and a space has the same name as an existing one in the XWiki instance, the content of that space will be overwritten and may be lost. For example, if a Confluence space with the key FAQ is imported using the default settings, it will overwrite the existing FAQ space and may even partially overwrite the FAQ application (at least its home page).

The decided solution for handling this issue is to define, as a parameter for input filter stream, a list of forbidden spaces: spaces that must never be overwritten. If a conflict occurs when importing a space whose key matches an existing one, the Confluence space will be renamed, based on a parameter that defines the renaming structure. Additionally, we have defined a way (using a input filter stream parameter) to handle spaces that are not in the forbidden list, giving us more control over what happens when there are conflicts between space names. For this, we introduce overwrite protection modes for spaces that may cause conflicts during the import of a Confluence package. The overwrite protection modes include Overwrite none of the existing spaces, Overwrite only spaces that were previously imported from Confluence, Overwrite only spaces that are not system spaces (not implemented in the current solution), Overwrite any space. If overwriting is allowed according to the selected protection mode, the renaming will still be applied.