Use constants in our list of accepted values

Use the constants we have already defined from the Connect SDK (apply to both Connect and CLI clients) to be more consistent and reduce amount of magic strings used in our codebase.

internal/provider/const.go

@@ -1,5 +1,11 @@
 package provider
 
+import (
+	"strings"
+
+	op "github.com/1Password/connect-sdk-go/onepassword"
+)
+
 const (
 	terraformItemIDDescription = "The Terraform resource identifier for this item in the format `vaults/<vault_id>/items/<item_id>`."
 
@@ -44,8 +50,29 @@ const (
 )
 
 var (
-	categories    = []string{"login", "password", "database"}
-	dbTypes       = []string{"db2", "filemaker", "msaccess", "mssql", "mysql", "oracle", "postgresql", "sqlite", "other"}
-	fieldPurposes = []string{"USERNAME", "PASSWORD", "NOTES"}
-	fieldTypes    = []string{"STRING", "EMAIL", "CONCEALED", "URL", "OTP", "DATE", "MONTH_YEAR", "MENU", "PHONE"}
+	dbTypes = []string{"db2", "filemaker", "msaccess", "mssql", "mysql", "oracle", "postgresql", "sqlite", "other"}
+
+	categories = []string{
+		strings.ToLower(string(op.Login)),
+		strings.ToLower(string(op.Password)),
+		strings.ToLower(string(op.Database)),
+	}
+
+	fieldPurposes = []string{
+		string(op.FieldPurposeUsername),
+		string(op.FieldPurposePassword),
+		string(op.FieldPurposeNotes),
+	}
+
+	fieldTypes = []string{
+		string(op.FieldTypeString),
+		string(op.FieldTypeConcealed),
+		string(op.FieldTypeEmail),
+		string(op.FieldTypeURL),
+		string(op.FieldTypeOTP),
+		string(op.FieldTypeDate),
+		string(op.FieldTypeMonthYear),
+		string(op.FieldTypeMenu),
+		string(op.FieldTypePhone),
+	}
 )