REFACTOR: Add diff2 enable flag to all DNS providers (#1851)

This should enable the diff2 code to be inserted with good "git blame" results for new code.  I'm adding this early to catch any problems early.

providers/oracle/oracleProvider.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/StackExchange/dnscontrol/v3/models"
 	"github.com/StackExchange/dnscontrol/v3/pkg/diff"
+	"github.com/StackExchange/dnscontrol/v3/pkg/diff2"
 	"github.com/StackExchange/dnscontrol/v3/pkg/printer"
 	"github.com/StackExchange/dnscontrol/v3/pkg/txtutil"
 	"github.com/StackExchange/dnscontrol/v3/providers"
@@ -239,75 +240,83 @@ func (o *oracleProvider) GetDomainCorrections(dc *models.DomainConfig) ([]*model
 		}
 	}
 
-	differ := diff.New(dc)
-	_, create, dels, modify, err := differ.IncrementalDiff(existingRecords)
-	if err != nil {
-		return nil, err
-	}
+	var corrections []*models.Correction
+	if !diff2.EnableDiff2 || true { // Remove "|| true" when diff2 version arrives
 
-	/*
-		Oracle's API doesn't have a way to update an existing record.
-		You can either update an existing RRSet, Domain (FQDN), or Zone in which you have to supply
-		the entire desired state, or you can patch specifying ADD/REMOVE actions.
-		Oracle's API is also increadibly slow, so updating individual RRSets is unbearably slow
-		for any size zone.
-	*/
-
-	corrections := []*models.Correction{}
-
-	if len(create) > 0 {
-		createRecords := models.Records{}
-		desc := ""
-		for _, d := range create {
-			createRecords = append(createRecords, d.Desired)
-			desc += d.String() + "\n"
+		differ := diff.New(dc)
+		_, create, dels, modify, err := differ.IncrementalDiff(existingRecords)
+		if err != nil {
+			return nil, err
 		}
-		desc = desc[:len(desc)-1]
 
-		corrections = append(corrections, &models.Correction{
-			Msg: desc,
-			F: func() error {
-				return o.patch(createRecords, nil, domain)
-			},
-		})
-	}
+		/*
+			Oracle's API doesn't have a way to update an existing record.
+			You can either update an existing RRSet, Domain (FQDN), or Zone in which you have to supply
+			the entire desired state, or you can patch specifying ADD/REMOVE actions.
+			Oracle's API is also increadibly slow, so updating individual RRSets is unbearably slow
+			for any size zone.
+		*/
 
-	if len(dels) > 0 {
-		deleteRecords := models.Records{}
-		desc := ""
-		for _, d := range dels {
-			deleteRecords = append(deleteRecords, d.Existing)
-			desc += d.String() + "\n"
+		corrections := []*models.Correction{}
+
+		if len(create) > 0 {
+			createRecords := models.Records{}
+			desc := ""
+			for _, d := range create {
+				createRecords = append(createRecords, d.Desired)
+				desc += d.String() + "\n"
+			}
+			desc = desc[:len(desc)-1]
+
+			corrections = append(corrections, &models.Correction{
+				Msg: desc,
+				F: func() error {
+					return o.patch(createRecords, nil, domain)
+				},
+			})
 		}
-		desc = desc[:len(desc)-1]
 
-		corrections = append(corrections, &models.Correction{
-			Msg: desc,
-			F: func() error {
-				return o.patch(nil, deleteRecords, domain)
-			},
-		})
-	}
+		if len(dels) > 0 {
+			deleteRecords := models.Records{}
+			desc := ""
+			for _, d := range dels {
+				deleteRecords = append(deleteRecords, d.Existing)
+				desc += d.String() + "\n"
+			}
+			desc = desc[:len(desc)-1]
 
-	if len(modify) > 0 {
-		createRecords := models.Records{}
-		deleteRecords := models.Records{}
-		desc := ""
-		for _, d := range modify {
-			createRecords = append(createRecords, d.Desired)
-			deleteRecords = append(deleteRecords, d.Existing)
-			desc += d.String() + "\n"
+			corrections = append(corrections, &models.Correction{
+				Msg: desc,
+				F: func() error {
+					return o.patch(nil, deleteRecords, domain)
+				},
+			})
 		}
-		desc = desc[:len(desc)-1]
 
-		corrections = append(corrections, &models.Correction{
-			Msg: desc,
-			F: func() error {
-				return o.patch(createRecords, deleteRecords, domain)
-			},
-		})
+		if len(modify) > 0 {
+			createRecords := models.Records{}
+			deleteRecords := models.Records{}
+			desc := ""
+			for _, d := range modify {
+				createRecords = append(createRecords, d.Desired)
+				deleteRecords = append(deleteRecords, d.Existing)
+				desc += d.String() + "\n"
+			}
+			desc = desc[:len(desc)-1]
+
+			corrections = append(corrections, &models.Correction{
+				Msg: desc,
+				F: func() error {
+					return o.patch(createRecords, deleteRecords, domain)
+				},
+			})
+		}
+
+		return corrections, nil
 	}
 
+	// Insert Future diff2 version here.
+
 	return corrections, nil
 }