Fixes #1007 by updating JUnit to 5.5.2 (#1015)

The missing class PreconditionViolationException is contained in
junit-platform-commons which comes in transitively by this JUnit
version. junit-jupiter-api had to be added because
spring-boot-dependencies imports an older version of this dependency.

pom.xml

@@ -39,7 +39,7 @@
         <spring-data.version>2.0.14.RELEASE</spring-data.version>
         <h2.version>1.4.190</h2.version>
         <junit.version>4.12</junit.version>
-        <junit-jupiter.version>5.0.2</junit-jupiter.version>
+        <junit-jupiter.version>5.5.2</junit-jupiter.version>
         <junit-vintage.version>${junit.version}.2</junit-vintage.version>
         <sping-test-junit5.version>1.0.2</sping-test-junit5.version>
         <compiler.version>3.8.1</compiler.version>
@@ -242,6 +242,12 @@
                 <version>${junit.version}</version>
                 <scope>test</scope>
             </dependency>
+            <dependency>
+                <groupId>org.junit.jupiter</groupId>
+                <artifactId>junit-jupiter-api</artifactId>
+                <version>${junit-jupiter.version}</version>
+                <scope>test</scope>
+            </dependency>
             <dependency>
                 <groupId>org.junit.jupiter</groupId>
                 <artifactId>junit-jupiter-engine</artifactId>