Update mssql's contained_db field to accept a boolean (hashicorp#13469)

Previously the `contained_db` parameter would only accept a string value
despite the fact that field type is documented as a boolean.

changelog/13469.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+secrets/database/mssql: Accept a boolean for `contained_db`, rather than just a string.
+```

plugins/database/mssql/mssql.go

@@ -5,13 +5,14 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
-	"strconv"
 	"strings"
 
 	_ "github.com/denisenkom/go-mssqldb"
-	multierror "github.com/hashicorp/go-multierror"
+	"github.com/hashicorp/go-multierror"
+	"github.com/hashicorp/go-secure-stdlib/parseutil"
 	"github.com/hashicorp/go-secure-stdlib/strutil"
-	dbplugin "github.com/hashicorp/vault/sdk/database/dbplugin/v5"
+
+	"github.com/hashicorp/vault/sdk/database/dbplugin/v5"
 	"github.com/hashicorp/vault/sdk/database/helper/connutil"
 	"github.com/hashicorp/vault/sdk/database/helper/dbutil"
 	"github.com/hashicorp/vault/sdk/helper/dbtxn"
@@ -98,20 +99,14 @@ func (m *MSSQL) Initialize(ctx context.Context, req dbplugin.InitializeRequest)
 		return dbplugin.InitializeResponse{}, fmt.Errorf("invalid username template - did you reference a field that isn't available? : %w", err)
 	}
 
-	containedDB := false
-	containedDBRaw, err := strutil.GetString(req.Config, "contained_db")
-	if err != nil {
-		return dbplugin.InitializeResponse{}, fmt.Errorf("failed to retrieve contained_db: %w", err)
-	}
-	if containedDBRaw != "" {
-		containedDB, err = strconv.ParseBool(containedDBRaw)
+	if v, ok := req.Config["contained_db"]; ok {
+		containedDB, err := parseutil.ParseBool(v)
 		if err != nil {
-			return dbplugin.InitializeResponse{}, fmt.Errorf("parsing error: incorrect boolean operator provided for contained_db: %w", err)
+			return dbplugin.InitializeResponse{}, fmt.Errorf(`invalid value for "contained_db": %w`, err)
 		}
+		m.containedDB = containedDB
 	}
 
-	m.containedDB = containedDB
-
 	resp := dbplugin.InitializeResponse{
 		Config: newConf,
 	}

plugins/database/mssql/mssql_test.go

@@ -11,7 +11,7 @@ import (
 	"time"
 
 	mssqlhelper "github.com/hashicorp/vault/helper/testhelpers/mssql"
-	dbplugin "github.com/hashicorp/vault/sdk/database/dbplugin/v5"
+	"github.com/hashicorp/vault/sdk/database/dbplugin/v5"
 	dbtesting "github.com/hashicorp/vault/sdk/database/dbplugin/v5/testing"
 	"github.com/hashicorp/vault/sdk/helper/dbtxn"
 )
@@ -43,6 +43,15 @@ func TestInitialize(t *testing.T) {
 			},
 		},
 		"contained_db set": {
+			dbplugin.InitializeRequest{
+				Config: map[string]interface{}{
+					"connection_url": connURL,
+					"contained_db":   true,
+				},
+				VerifyConnection: true,
+			},
+		},
+		"contained_db set string": {
 			dbplugin.InitializeRequest{
 				Config: map[string]interface{}{
 					"connection_url": connURL,