docs: add migration guide for v4 (#220)

* docs: add migration guide for v4

Signed-off-by: Dustin Popp <[email protected]>

Co-authored-by: Phil Adams <[email protected]>

Author: dpopp07

MIGRATION-V1.md

@@ -0,0 +1,55 @@
+# Migration Guide for v4
+
+## Breaking Changes
+
+### Node Version
+Node versions 12 is longer supported - 14 is the minimum version supported.
+
+### TypeScript Version
+The `typescript` development dependnecy is now required to be at least version 4.
+
+Run `npm install -D typescript@4` to upgrade to version 4.
+
+Code produced by the IBM OpenAPI SDK Generator should already be compliant with TypeScript v4.
+
+Additionally, you may need to upgrade `@typescript-eslint/eslint-plugin` to be compatible with the new
+version of TypeScript. This upgrade should be safe and compatible, especially if you remain on major version 4
+of this development dependency.
+
+Run `npm i -D '@typescript-eslint/eslint-plugin'` to upgrade.
+
+### Jest Version
+The `jest` development dependency is now required to be at least version 29.
+
+Run `npm install -D jest@29` to upgrade to version 29.
+
+Code produced by the IBM OpenAPI Generator should already be compliant with Jest v29.
+
+Note: Ensure your test code does not contain the anti-pattern of using a `done` callback with an `async` function.
+This is no longer permitted in Jest 29, whereas it was discouraged but permitted in previous versions. An old version of the IBM OpenAPI SDK Generator included a bug that generated this pattern. If your generated test code has not been updated since then, you may run into this issue.
+
+Example diff showing proper resolution:
+```
+diff --git a/test/integration/example.v1.test.js b/test/integration/example.v1.test.js
+index be0bec3..62f03f8 100644
+--- a/test/integration/example.v1.test.js
++++ b/test/integration/example.v1.test.js
+@@ -38,7 +38,7 @@ describe('ExampleV1_integration', () => {
+   jest.setTimeout(timeout);
+   let example;
+ 
+-  beforeAll(async (done) => {
++  beforeAll(async () => {
+     example = ExampleV1.newInstance({});
+ 
+     const config = readExternalSources(ExampleV1.DEFAULT_SERVICE_NAME);
+@@ -58,8 +58,6 @@ describe('ExampleV1_integration', () => {
+ 
+     log(`Service URL: ${example.baseOptions.serviceUrl}`);
+     log('Finished setup.');
+-
+-    done();
+   });
+ 
+   test('getSomething()', async () => {
+```