feat: allow machine user id to be set during creation (#8265)

# Which Problems Are Solved
Solves the problem described in #8264.

# How the Problems Are Solved

Added a UserID field which can be set during Machine User creation.

# Additional Changes

Added addition unit and integration tests to cover the cases where a
UserID field is present.

# Additional Context

- Closes #8264

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>

internal/command/user_machine_test.go

@@ -148,6 +148,52 @@ func TestCommandSide_AddMachine(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "add machine - custom id, ok",
+			fields: fields{
+				eventstore: eventstoreExpect(
+					t,
+					expectFilter(),
+					expectFilter(
+						eventFromEventPusher(
+							org.NewDomainPolicyAddedEvent(context.Background(),
+								&user.NewAggregate("optionalID1", "org1").Aggregate,
+								true,
+								true,
+								true,
+							),
+						),
+					),
+					expectPush(
+						user.NewMachineAddedEvent(context.Background(),
+							&user.NewAggregate("optionalID1", "org1").Aggregate,
+							"username",
+							"name",
+							"description",
+							true,
+							domain.OIDCTokenTypeBearer,
+						),
+					),
+				),
+			},
+			args: args{
+				ctx: context.Background(),
+				machine: &Machine{
+					ObjectRoot: models.ObjectRoot{
+						AggregateID:   "optionalID1",
+						ResourceOwner: "org1",
+					},
+					Description: "description",
+					Name:        "name",
+					Username:    "username",
+				},
+			},
+			res: res{
+				want: &domain.ObjectDetails{
+					ResourceOwner: "org1",
+				},
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {