Name the credential tool of a software-issued offer in the plan (issue 928)

internal/catalogue/resolve.go

@@ -230,6 +230,8 @@ type Needed struct {
 	// CredentialForm is the credential form the provider's offer declares (Manifest.CredentialFormOf, issue 768),
 	// named in a handed consumer's plan for the vault; empty where the provider's manifest is not in hand.
 	CredentialForm string
+	// CredentialTool is the tool of the offer that the provider's software issues the credential through (issue 928).
+	CredentialTool string
 	// Manager is set when this holder is a refreshable-grant licence's MANAGER, delivered the refresh
 	// token rather than an access token (novox/hq ADR 0050). It changes one thing downstream: an empty
 	// Sealed is tolerated — the manager has not adopted a refresh token yet, which is a real waiting
@@ -543,7 +545,7 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 				needs = append(needs, Needed{
 					Name: want, From: node.Name, At: at, Module: by.Module,
 					Serves: servedByOne(by, want), For: because[want],
-					SharedOwn: sharedByOne(by, want), CredentialForm: by.CredentialFormOf(want),
+					SharedOwn: sharedByOne(by, want), CredentialForm: by.CredentialFormOf(want), CredentialTool: by.CredentialToolOf(want),
 					Identity: by.IdentityBoundOf(want)})
 			} else if served := servedByOne(by, want); len(served) > 0 {
 				// Answered here with no credential to mint, but the provider serves facts the
@@ -565,7 +567,7 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 				}
 				needs = append(needs, Needed{
 					Name: want, From: node.Name, At: at, Serves: served, For: because[want], Module: by.Module,
-					CredentialForm: by.CredentialFormOf(want)})
+					CredentialForm: by.CredentialFormOf(want), CredentialTool: by.CredentialToolOf(want)})
 			}
 			continue
 		}
@@ -594,17 +596,17 @@ func Resolve(catalogue map[string]Manifest, assigned []string, node Node, world
 						node.Name, want, p.Node, meshNetwork))
 					return
 				}
-				shared, form := "", ""
+				shared, form, tool := "", "", ""
 				// A provider whose definition is not in hand is held to the tightest bound the
 				// mesh knows, not to none: what it keeps is not known here (ADR 0225).
 				bound := DefaultIdentityBound
 				if pm, known := catalogue[p.Module]; known {
 					shared, _ = pm.SharedCredentialOf(want)
-					form = pm.CredentialFormOf(want)
+					form, tool = pm.CredentialFormOf(want), pm.CredentialToolOf(want)
 					bound = pm.IdentityBoundOf(want)
 				}
 				needs = append(needs, Needed{Name: want, From: p.Node, At: p.At, Module: p.Module,
-					Serves: p.Serves, For: because[want], SharedOwn: shared, CredentialForm: form, Identity: bound,
+					Serves: p.Serves, For: because[want], SharedOwn: shared, CredentialForm: form, CredentialTool: tool, Identity: bound,
 					LeftOut: p.LeftOut})
 			}
 			switch {