Add third-party self-referential relations

Introduce a self-referential many-to-many relation table so a
third party can have child third parties. Each relation is
directional (parent to child); both directions can coexist as
independent rows.

Add a first_level boolean on third_parties (default true) with
a filter on the list page that defaults to showing only
first-level third parties.

Frontend adds a "Third Parties" tab on the detail page where
users can link existing third parties or create new ones from
the common third party catalog (created as non-first-level).
The list page gets a First Level/All toggle filter.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/server/api/console/v1/graphql/organization.graphql

@@ -331,6 +331,7 @@ type Organization implements Node {
         last: Int
         before: CursorKey
         orderBy: ThirdPartyOrder
+        filter: ThirdPartyFilter
     ): ThirdPartyConnection! @goField(forceResolver: true)
 
     thirdPartiesDocument: Document @goField(forceResolver: true)