Use constants for field names

Author: PerthCharern

src/Microsoft.OpenApi.Readers/V2/OpenApiHeaderDeserializer.cs

@@ -137,7 +137,7 @@ internal static partial class OpenApiV2Deserializer
             new AnyFieldMap<OpenApiHeader>
             {
                 {
-                    "default",
+                    OpenApiConstants.Default,
                     new AnyFieldMapParameter<OpenApiHeader>(
                         p => p.Schema.Default,
                         (p, v) => p.Schema.Default = v,
@@ -149,7 +149,7 @@ internal static partial class OpenApiV2Deserializer
             new AnyListFieldMap<OpenApiHeader>
             {
                 {
-                    "enum",
+                    OpenApiConstants.Enum,
                     new AnyListFieldMapParameter<OpenApiHeader>(
                         p => p.Schema.Enum,
                         (p, v) => p.Schema.Enum = v,

src/Microsoft.OpenApi.Readers/V2/OpenApiParameterDeserializer.cs

@@ -147,7 +147,7 @@ internal static partial class OpenApiV2Deserializer
             new AnyFieldMap<OpenApiParameter>
             {
                 {
-                    "default",
+                    OpenApiConstants.Default,
                     new AnyFieldMapParameter<OpenApiParameter>(
                         p => p.Schema.Default,
                         (p, v) => p.Schema.Default = v,
@@ -159,7 +159,7 @@ internal static partial class OpenApiV2Deserializer
             new AnyListFieldMap<OpenApiParameter>
             {
                 {
-                    "enum",
+                    OpenApiConstants.Enum,
                     new AnyListFieldMapParameter<OpenApiParameter>(
                         p => p.Schema.Enum,
                         (p, v) => p.Schema.Enum = v,

src/Microsoft.OpenApi.Readers/V2/OpenApiSchemaDeserializer.cs

@@ -211,13 +211,30 @@ internal static partial class OpenApiV2Deserializer
 
         private static readonly AnyFieldMap<OpenApiSchema> _schemaAnyFields = new AnyFieldMap<OpenApiSchema>
         {
-            { "default", new AnyFieldMapParameter<OpenApiSchema>(s => s.Default, (s, v) => s.Default = v, s => s) },
-            { "example", new AnyFieldMapParameter<OpenApiSchema>(s => s.Example, (s, v) => s.Example = v, s => s) }
+            {
+                OpenApiConstants.Default,
+                new AnyFieldMapParameter<OpenApiSchema>(
+                    s => s.Default, 
+                    (s, v) => s.Default = v, 
+                    s => s)
+            },
+            {
+                OpenApiConstants.Example,
+                new AnyFieldMapParameter<OpenApiSchema>(
+                    s => s.Example, 
+                    (s, v) => s.Example = v, 
+                    s => s) }
         };
 
         private static readonly AnyListFieldMap<OpenApiSchema> _schemaAnyListFields = new AnyListFieldMap<OpenApiSchema>
         {
-            { "enum", new AnyListFieldMapParameter<OpenApiSchema>(s => s.Enum, (s, v) => s.Enum = v, s => s) }
+            {
+                OpenApiConstants.Enum,
+                new AnyListFieldMapParameter<OpenApiSchema>(
+                    s => s.Enum, 
+                    (s, v) => s.Enum = v, 
+                    s => s)
+            }
         };
 
         public static OpenApiSchema LoadSchema(ParseNode node)

src/Microsoft.OpenApi.Readers/V3/OpenApiSchemaDeserializer.cs

@@ -246,14 +246,14 @@ internal static partial class OpenApiV3Deserializer
         private static readonly AnyFieldMap<OpenApiSchema> _schemaAnyFields = new AnyFieldMap<OpenApiSchema>
         {
             {
-                "default",
+                OpenApiConstants.Default,
                 new AnyFieldMapParameter<OpenApiSchema>(
                     s => s.Default,
                     (s, v) => s.Default = v,
                     s => s)
             },
             {
-                "example",
+                 OpenApiConstants.Example,
                 new AnyFieldMapParameter<OpenApiSchema>(
                     s => s.Example, 
                     (s, v) => s.Example = v, 
@@ -263,7 +263,13 @@ internal static partial class OpenApiV3Deserializer
 
         private static readonly AnyListFieldMap<OpenApiSchema> _schemaAnyListFields = new AnyListFieldMap<OpenApiSchema>
         {
-            { "enum", new AnyListFieldMapParameter<OpenApiSchema>(s => s.Enum, (s, v) => s.Enum = v, s => s) }
+            {
+                OpenApiConstants.Enum,
+                new AnyListFieldMapParameter<OpenApiSchema>(
+                    s => s.Enum, 
+                    (s, v) => s.Enum = v,
+                    s => s)
+            }
         };
 
         public static OpenApiSchema LoadSchema(ParseNode node)