add features section to graphql proxy config (#6298)

### **User description**
This PR adds a new `features` section to the GraphQL proxy
configuration. It will allow the enable or disable specific features for
proxy-only mode.

## Types of changes

<!-- What types of changes does your code introduce? Put an `x` in all
the boxes that apply: -->

- [ ] Bug fix (non-breaking change which fixes an issue)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Refactoring or add test (improvements in base code or adds test
coverage to functionality)


___

### **PR Type**
Enhancement


___

### **Description**
This PR introduces a new `features` section to the GraphQL proxy
configuration:
- Added `features` section to `GraphQLProxyConfig` in
`apidef/api_definitions.go`.
- Introduced `GraphQLProxyFeaturesConfig` struct with
`UseImmutableHeaders` field.
- Updated `DummyAPI` function to include default `features`
configuration.
- Updated GraphQL proxy schema in `apidef/schema.go` to include
`features` section with `use_immutable_headers` property.


___



### **Changes walkthrough** 📝
<table><thead><tr><th></th><th align="left">Relevant
files</th></tr></thead><tbody><tr><td><strong>Enhancement
</strong></td><td><table>
<tr>
  <td>
    <details>
<summary><strong>api_definitions.go</strong><dd><code>Add features
section to GraphQL proxy configuration.</code>&nbsp; &nbsp; &nbsp;
&nbsp; &nbsp; </dd></summary>
<hr>

apidef/api_definitions.go
<li>Added <code>features</code> section to
<code>GraphQLProxyConfig</code>.<br> <li> Introduced
<code>GraphQLProxyFeaturesConfig</code> struct with
<code>UseImmutableHeaders</code> <br>field.<br> <li> Updated
<code>DummyAPI</code> function to include default <code>features</code>
configuration.<br>


</details>
    

  </td>
<td><a
href="https://github.com/TykTechnologies/tyk/pull/6298/files#diff-9961ccc89a48d32db5b47ba3006315ef52f6e5007fb4b09f8c5d6d299c669d67">+10/-0</a>&nbsp;
&nbsp; </td>
</tr>                    

<tr>
  <td>
    <details>
<summary><strong>schema.go</strong><dd><code>Update GraphQL proxy schema
with features section.</code>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
&nbsp; </dd></summary>
<hr>

apidef/schema.go
<li>Added <code>features</code> section to GraphQL proxy schema.<br>
<li> Included <code>use_immutable_headers</code> property in the
schema.<br>


</details>
    

  </td>
<td><a
href="https://github.com/TykTechnologies/tyk/pull/6298/files#diff-f8a37bb370eb6fe20063786a5e6ea3d85a5c91d8e289f0b3e045830c4d322095">+8/-0</a>&nbsp;
&nbsp; &nbsp; </td>
</tr>                    
</table></td></tr></tr></tbody></table>

___

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apidef/adapter/asyncapi_test.go

@@ -321,6 +321,9 @@ const expectedGraphqlConfig = `{
         "global_headers": null
     },
     "proxy": {
+        "features": {
+            "use_immutable_headers": false
+        },
         "auth_headers": {},
         "request_headers": null,
         "use_response_extensions": {

apidef/adapter/openapi_test.go

@@ -302,6 +302,9 @@ const expectedOpenAPIGraphQLConfig = `{
         "global_headers": null
     },
     "proxy": {
+        "features": {
+            "use_immutable_headers": false
+        },
         "auth_headers": {},
         "request_headers": null,
         "use_response_extensions": {

apidef/api_definitions.go

@@ -13,13 +13,15 @@ import (
 	"github.com/lonelycode/osin"
 
 	"github.com/TykTechnologies/storage/persistent/model"
+
 	"github.com/TykTechnologies/tyk/internal/event"
 
 	"github.com/TykTechnologies/tyk/internal/reflect"
 
 	"github.com/TykTechnologies/graphql-go-tools/pkg/execution/datasource"
 
 	"github.com/TykTechnologies/gojsonschema"
+
 	"github.com/TykTechnologies/tyk/regexp"
 
 	"github.com/TykTechnologies/tyk/internal/uuid"
@@ -847,13 +849,18 @@ type GraphQLResponseExtensions struct {
 }
 
 type GraphQLProxyConfig struct {
+	Features              GraphQLProxyFeaturesConfig             `bson:"features" json:"features"`
 	AuthHeaders           map[string]string                      `bson:"auth_headers" json:"auth_headers"`
 	SubscriptionType      SubscriptionType                       `bson:"subscription_type" json:"subscription_type,omitempty"`
 	RequestHeaders        map[string]string                      `bson:"request_headers" json:"request_headers"`
 	UseResponseExtensions GraphQLResponseExtensions              `bson:"use_response_extensions" json:"use_response_extensions"`
 	RequestHeadersRewrite map[string]RequestHeadersRewriteConfig `json:"request_headers_rewrite" bson:"request_headers_rewrite"`
 }
 
+type GraphQLProxyFeaturesConfig struct {
+	UseImmutableHeaders bool `bson:"use_immutable_headers" json:"use_immutable_headers"`
+}
+
 type RequestHeadersRewriteConfig struct {
 	Value  string `json:"value" bson:"value"`
 	Remove bool   `json:"remove" bson:"remove"`
@@ -1294,6 +1301,9 @@ func DummyAPI() APIDefinition {
 		Version:          GraphQLConfigVersion2,
 		LastSchemaUpdate: nil,
 		Proxy: GraphQLProxyConfig{
+			Features: GraphQLProxyFeaturesConfig{
+				UseImmutableHeaders: true,
+			},
 			AuthHeaders: map[string]string{},
 		},
 	}

apidef/oas/oas_test.go

@@ -281,6 +281,7 @@ func TestOAS_ExtractTo_ResetAPIDefinition(t *testing.T) {
 		"APIDefinition.GraphQL.Engine.DataSources[0].Config[0]",
 		"APIDefinition.GraphQL.Engine.GlobalHeaders[0].Key",
 		"APIDefinition.GraphQL.Engine.GlobalHeaders[0].Value",
+		"APIDefinition.GraphQL.Proxy.Features.UseImmutableHeaders",
 		"APIDefinition.GraphQL.Proxy.AuthHeaders[0]",
 		"APIDefinition.GraphQL.Proxy.SubscriptionType",
 		"APIDefinition.GraphQL.Proxy.RequestHeaders[0]",

apidef/schema.go

@@ -641,6 +641,14 @@ const Schema = `{
                 "proxy": {
                     "type": ["object", "null"],
                     "properties": {
+						"features": {
+							"type": ["object", "null"],
+							"properties": {
+								"use_immutable_headers": {
+									"type": "boolean"
+								}
+							}
+						},
                         "auth_headers": {
                             "type": ["object", "null"]
                         },