Test build against JDK 15 (#182)

* Test build against JDK 15

* deploy-sonatype - don't treat username as a secret

* settings.xml - username is not a secret

.github/settings.xml

@@ -3,12 +3,12 @@
     <servers>
         <server>
             <id>sonatype-nexus-snapshots</id>
-            <username>${env.NEXUS_USERNAME}</username>
+            <username>kemitix</username>
             <password>${env.NEXUS_PASSWORD}</password>
         </server>
         <server>
             <id>sonatype-nexus-staging</id>
-            <username>${env.NEXUS_USERNAME}</username>
+            <username>kemitix</username>
             <password>${env.NEXUS_PASSWORD}</password>
         </server>
     </servers>

.github/workflows/build-maven.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [ 8, 11, 14 ]
+        java: [ 8, 11, 15 ]
     steps:
       - uses: kamiazya/setup-graphviz@v1
       - uses: actions/checkout@v2

.github/workflows/deploy-sonatype.yml

@@ -34,7 +34,6 @@ jobs:
             -B \
             deploy
         env:
-          NEXUS_USERNAME: ${{ secrets.NEXUS_USERNAME }}
           NEXUS_PASSWORD: ${{ secrets.NEXUS_PASSWORD }}
           GPG_KEYNAME: ${{ secrets.GPG_KEYNAME }}
           GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}