Add importThirdPartyFromCommon GraphQL mutation

Expose the explicit import action over the console API. The mutation
takes an organization and a common third party, authorizes as a
third-party create, and delegates to ThirdPartyService.ImportFromCommon,
returning the org ThirdParty edge plus a created flag so the client can
tell a fresh import from a re-import.

Add an end-to-end test covering the two behaviours that matter: the
first import seeds the org vendor from the catalog and backfills the
linked tracker pattern's third_party_id, and a second import is
idempotent, returning the same row with created=false.

The gqlgen-generated types and execution code are build artifacts (not
tracked), so only the schema and the resolver change here.

Signed-off-by: Émile Ré <emile@probo.com>

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

@@ -454,6 +454,9 @@ type ThirdPartyRiskAssessmentEdge {
 
 extend type Mutation {
     createThirdParty(input: CreateThirdPartyInput!): CreateThirdPartyPayload!
+    importThirdPartyFromCommon(
+        input: ImportThirdPartyFromCommonInput!
+    ): ImportThirdPartyFromCommonPayload!
     updateThirdParty(input: UpdateThirdPartyInput!): UpdateThirdPartyPayload!
     deleteThirdParty(input: DeleteThirdPartyInput!): DeleteThirdPartyPayload!
     createThirdPartyContact(
@@ -672,10 +675,20 @@ input VetThirdPartyInput {
     procedure: String
 }
 
+input ImportThirdPartyFromCommonInput {
+    organizationId: ID!
+    commonThirdPartyId: ID!
+}
+
 type CreateThirdPartyPayload {
     thirdPartyEdge: ThirdPartyEdge!
 }
 
+type ImportThirdPartyFromCommonPayload {
+    thirdPartyEdge: ThirdPartyEdge!
+    created: Boolean!
+}
+
 type UpdateThirdPartyPayload {
     thirdParty: ThirdParty!
 }