Enabled setting custom 'User-Agent' header in Admin API SDK

refs https://github.com/TryGhost/Toolbox/issues/348
refs https://github.com/TryGhost/Toolbox/issues/301

- Allows for a full control over the 'User-Agent' header. Enables customizing the header in whatever way the client needs (for example prepending a value when there's a wrapping library using the SDK)

Author: naz

packages/admin-api/lib/admin-api.js

@@ -41,7 +41,7 @@ const resolveAPIPrefix = (version) => {
  * @param {String} options.url
  * @param {String} [options.ghostPath]
  * @param {String|Boolean} options.version - a version string like v3.2, v4.1, v5.8 or boolean value identifying presence of Accept-Version header
- * @param {Boolean} [options.userAgent] - flag controlling if the 'User-Agent' header should be sent with a request
+ * @param {String|Boolean} [options.userAgent] - flag controlling if the 'User-Agent' header should be sent with a request
  * @param {Function} [options.makeRequest]
  * @param {Function} [options.generateToken]
  */
@@ -417,7 +417,11 @@ module.exports = function GhostAdminAPI(options) {
         };
 
         if (config.userAgent) {
-            ghostHeaders['User-Agent'] = `GhostAdminSDK/${packageVersion}`;
+            if (typeof config.userAgent === 'boolean') {
+                ghostHeaders['User-Agent'] = `GhostAdminSDK/${packageVersion}`;
+            } else {
+                headers['User-Agent'] = config.userAgent;
+            }
         }
 
         if (config.acceptVersionHeader) {

packages/admin-api/test/lib/admin-api.test.js

@@ -291,7 +291,7 @@ describe('GhostAdminAPI general', function () {
             should.equal(generateTokenSpy.args[0][1], '/admin/');
         });
 
-        it('does not set  "User-Agent" header when disabled', async function () {
+        it('does not set "User-Agent" header when disabled', async function () {
             const makeRequestStub = sinon.stub().returns(Promise.resolve({
                 config: {}
             }));
@@ -314,5 +314,29 @@ describe('GhostAdminAPI general', function () {
             should.equal(generateTokenSpy.args[0][0], '5c73def7a21ad85eda5d4faa:d9a3e5b2d6c2a4afb094655c4dc543220be60b3561fa9622e3891213cb4357d0');
             should.equal(generateTokenSpy.args[0][1], '/admin/');
         });
+
+        it('sets a custom value for "User-Agent" header', async function () {
+            const makeRequestStub = sinon.stub().returns(Promise.resolve({
+                config: {}
+            }));
+            const generateTokenSpy = sinon.spy();
+
+            const api = new GhostAdminAPI({
+                version: true,
+                url: `http://ghost.local`,
+                key: '5c73def7a21ad85eda5d4faa:d9a3e5b2d6c2a4afb094655c4dc543220be60b3561fa9622e3891213cb4357d0',
+                makeRequest: makeRequestStub,
+                generateToken: generateTokenSpy,
+                userAgent: 'Custom Value'
+            });
+
+            await api.config.read();
+
+            makeRequestStub.calledOnce.should.be.true();
+            should.equal(makeRequestStub.args[0][0].headers['Accept-Version'], 'v5.0');
+            should.equal(makeRequestStub.args[0][0].headers['User-Agent'], 'Custom Value');
+            should.equal(generateTokenSpy.args[0][0], '5c73def7a21ad85eda5d4faa:d9a3e5b2d6c2a4afb094655c4dc543220be60b3561fa9622e3891213cb4357d0');
+            should.equal(generateTokenSpy.args[0][1], '/admin/');
+        });
     });
 });