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/editor-ui/src/components/CredentialEdit/CredentialEdit.vue

@@ -412,7 +412,8 @@ export default defineComponent({
 			return (
 				!!this.credentialTypeName &&
 				(((this.credentialTypeName === 'oAuth2Api' || this.parentTypes.includes('oAuth2Api')) &&
-					this.credentialData.grantType === 'authorizationCode') ||
+					(this.credentialData.grantType === 'authorizationCode' ||
+						this.credentialData.grantType === 'pkce')) ||
 					this.credentialTypeName === 'oAuth1Api' ||
 					this.parentTypes.includes('oAuth1Api'))
 			);