Prepare for release v1.8.1 [updated] (#511)

prepared for release 1.8.1

docs/RELEASE_NOTES.md

@@ -36,24 +36,30 @@
 
 -->
 
-### 1.8.1 -  March 23, 2020
+### 1.8.1 -  April 22, 2020
 [Commits](https://github.com/commercetools/commercetools-sync-java/compare/1.8.0...1.8.1) |
 [Javadoc](https://commercetools.github.io/commercetools-sync-java/v/1.8.1/) | 
 [Jar](https://bintray.com/commercetools/maven/commercetools-sync-java/1.8.1)
 
 - ✨ **Enhancements** (1)
     - **Commons** - Remove final keyword on interface/abstract method params. [#165](https://github.com/commercetools/commercetools-sync-java/issues/165)
 
-- 🐞 **Bug Fixes** (1)
+- 🐞 **Bug Fixes** (3)
     - **CartDiscount Sync** - Fixed a bug in the `CartDiscountSync` which generates a `changeValue` action when there is no change, causing the sync to fail for that cart discount.
     Thanks, @michaelbannister, for the contributions! [#494](https://github.com/commercetools/commercetools-sync-java/issues/494)
+    - **Product Sync** - Fixed a bug in the `ProductSync` when `ensurePriceChannels` is enabled in ProductSyncOptions should not create a missing channel used on product variant price draft.
+        [#499](https://github.com/commercetools/commercetools-sync-java/issues/499)
+    - **Product/Category Sync** - Validate that asset keys are always defined on the supplied drafts and the existing target resources (products/categories).
+        [#366](https://github.com/commercetools/commercetools-sync-java/issues/366)
 
 - 🛠️ **Dependency Updates** (5)
-    - `junit.jupiterApiVersion` `5.5.2` ->  [`5.6.0`](https://github.com/junit-team/junit5/releases/tag/r5.6.0)
-    - `commercetools-jvm-sdk` `1.48.0` -> [`1.50.0`](http://commercetools.github.io/commercetools-jvm-sdk/apidocs/io/sphere/sdk/meta/ReleaseNotes.html#v1_50_0)
+    - `junit.jupiterApiVersion` `5.5.2` ->  [`5.6.1`](https://github.com/junit-team/junit5/releases/tag/r5.6.1)
+    - `commercetools-jvm-sdk` `1.48.0` -> [`1.51.0`](http://commercetools.github.io/commercetools-jvm-sdk/apidocs/io/sphere/sdk/meta/ReleaseNotes.html#v1_51_0)
     - `org.assertj.assertj-core` `3.14.0` ->  [`3.15.0`](https://assertj.github.io/doc/#assertj-core-3-15-0-release-notes)
     - `mockito-junit-jupiter` `3.2.4` -> [`3.3.3`](https://github.com/mockito/mockito/releases/tag/v3.3.3)
     - `com.github.ben-manes.versions` `0.27.0` -> [`0.28.0`](https://github.com/ben-manes/gradle-versions-plugin/releases/tag/v0.28.0) 
+    - `ru.vyarus.mkdocs` `2.0.0` -> [`2.0.1`](https://github.com/xvik/gradle-mkdocs-plugin/releases/tag/2.0.1) 
+    - `org.ajoberstar.grgit` `4.0.1` -> [`4.0.2`](https://github.com/ajoberstar/grgit/releases/tag/4.0.2) 
 
 ### 1.8.0 -  Jan 17, 2020
 [Commits](https://github.com/commercetools/commercetools-sync-java/compare/1.7.0...1.8.0) |