feat(core): Add PKCE for OAuth2 (#6324)

* Remove authorization header when empty

* Import pkce

* Add OAuth2 with new grant type to Twitter

* Add pkce logic auto assign authorization code if pkce not defined

* Add pkce to ui and interfaces

* Fix scopes for Oauth2 twitter

* Deubg + pass it through header

* Add debug console, add airtable cred

* Remove all console.logs, make PKCE in th body only when it exists

* Remove invalid character ~

* Remove more console.logs

* remove body inside query

* Remove useless grantype check

* Hide oauth2 twitter waiting for overhaul

* Remove redundant header removal

* Remove more console.logs

* Add comment for code verifier

* Remove uneeded scopes

* Restore client id in callback

* Revert "Add OAuth2 with new grant type to Twitter"

This reverts commit 1c3b331aa1974159d1ffe1a4fbf2050722f0f24c.

* Remove oauth2 from twitter

* Remove properties linked to oauth2

* Fix lodash imports

* remove redundant check

* remove redundant codeVerifier

* patch pkce-challenge to avoid generating `code_verifier` with `~`

* store `codeVerifier` on the DB like `csrfSecret`

* remove unrelated changes

---------

Co-authored-by: Marcus <marcus@n8n.io>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/nodes-base/credentials/OAuth2Api.credentials.ts

@@ -23,6 +23,10 @@ export class OAuth2Api implements ICredentialType {
 					name: 'Client Credentials',
 					value: 'clientCredentials',
 				},
+				{
+					name: 'PKCE',
+					value: 'pkce',
+				},
 			],
 			default: 'authorizationCode',
 		},
@@ -32,7 +36,7 @@ export class OAuth2Api implements ICredentialType {
 			type: 'string',
 			displayOptions: {
 				show: {
-					grantType: ['authorizationCode'],
+					grantType: ['authorizationCode', 'pkce'],
 				},
 			},
 			default: '',
@@ -74,7 +78,7 @@ export class OAuth2Api implements ICredentialType {
 			type: 'string',
 			displayOptions: {
 				show: {
-					grantType: ['authorizationCode'],
+					grantType: ['authorizationCode', 'pkce'],
 				},
 			},
 			default: '',