cloudapi/v2: tweak customizations

Fix verbiage of groups customization, fields which accept an array
should be plural.

Remove the sshkey customization, sshkeys are merged into user
customizations anyway, so users should use the "users" customization
instead.

Since these customizations aren't in use yet, this edit should be fine.

See #3716

internal/cloudapi/v2/compose.go

@@ -272,20 +272,9 @@ func (request *ComposeRequest) GetBlueprintWithCustomizations() (blueprint.Bluep
 		bp.Customizations.Kernel = kernel
 	}
 
-	if request.Customizations.Sshkey != nil {
-		keys := []blueprint.SSHKeyCustomization{}
-		for _, key := range *request.Customizations.Sshkey {
-			keys = append(keys, blueprint.SSHKeyCustomization{
-				User: key.User,
-				Key:  key.Key,
-			})
-		}
-		bp.Customizations.SSHKey = keys
-	}
-
-	if request.Customizations.Group != nil {
+	if request.Customizations.Groups != nil {
 		groups := []blueprint.GroupCustomization{}
-		for _, group := range *request.Customizations.Group {
+		for _, group := range *request.Customizations.Groups {
 			groups = append(groups, blueprint.GroupCustomization{
 				Name: group.Name,
 				GID:  group.Gid,

internal/cloudapi/v2/compose_test.go

@@ -120,12 +120,6 @@ func TestGetBlueprintWithCustomizations(t *testing.T) {
 				Url: "provisioning-url.local",
 			},
 		},
-		Sshkey: &[]SSHKey{
-			{
-				Key:  "key",
-				User: "user",
-			},
-		},
 		Timezone: &Timezone{
 			Timezone: common.ToPtr("US/Eastern"),
 			Ntpservers: common.ToPtr([]string{
@@ -226,12 +220,6 @@ func TestGetBlueprintWithCustomizations(t *testing.T) {
 				ProvisioningURL: "provisioning-url.local",
 			},
 		},
-		SSHKey: []blueprint.SSHKeyCustomization{
-			{
-				Key:  "key",
-				User: "user",
-			},
-		},
 		Timezone: &blueprint.TimezoneCustomization{
 			Timezone: common.ToPtr("US/Eastern"),
 			NTPServers: []string{