refactor: move common steps from auth into common

+ correct the feature description for getAuthorizationHeader

features/adapter_get-authorization-header.feature

-Feature: Does the adapter authenticate?
-  When an adapter instance is created it authenticates and receives a token
+Feature: Can the adapter create an authorization header?
+  The adapter getAuthorizationHeader method works as expected
 
   Scenario: getAuthorizationHeader returns a bearer token
     Given valid config

test/cucumber/adapter/auth.steps.js

 const assert = require('assert');
-const { Given, When, Then } = require('@cucumber/cucumber');
+const { When, Then } = require('@cucumber/cucumber');
 
 const { fixtures } = require('../../fixtures/server');
 
-const mockValidConfig = fixtures.get('config-valid');
-const mockInvalidConfig = fixtures.get('config-invalid');
-
-const mockSchema = require('../../mock/swagger.json');
-const { Adapter } = require('../../../dist/adapter');
-
-
-Given('valid config', function() {
-  this.config = mockValidConfig
-});
-
-When('the adapter instance is created', function() {
-  //let mockProtocol = new GenericProtocol(this.schema);
-  let mockAdapter = new Adapter(this.protocol, this.config);
-  this.adapter = mockAdapter;
-});
-
 When('the auth method is called', async function() {
   await this.adapter.auth();
 });
@@ -28,11 +11,6 @@ Then('the adapter credentials are populated', function() {
   assert.equal(this.adapter.credentials.token, fixtures.get('response-valid-token').token);
 });
 
-Given('invalid config', function() {
-  this.schema = mockSchema;
-  this.config = mockInvalidConfig;
-});
-
 Then('the adapter auth fails', function() {
   this.adapter.auth()
   .catch((error) => {

test/cucumber/adapter/common.steps.js

 const assert = require('assert');
-const { When, Then } = require('@cucumber/cucumber');
+const { Given, When, Then } = require('@cucumber/cucumber');
+
+const { fixtures } = require('../../fixtures/server');
+
+const mockValidConfig = fixtures.get('config-valid');
+const mockInvalidConfig = fixtures.get('config-invalid');
+const mockSchema = require('../../mock/swagger.json');
+const { Adapter } = require('../../../dist/adapter');
+
+Given('valid config', function() {
+  this.config = mockValidConfig
+});
+
+Given('invalid config', function() {
+  this.schema = mockSchema;
+  this.config = mockInvalidConfig;
+});
+
+When('the adapter instance is created', function() {
+  let mockAdapter = new Adapter(this.protocol, this.config);
+  this.adapter = mockAdapter;
+});
 
 Then('a successful response is returned with status {int}', function(expectedStatus) {
   this.call