Consistent reactor-core versions
Consistent reactor-core versions

Previously the IDE (STS) was resolving a different reactor-core
version (3.0.0.BUILD-SNAPSHOT) than the build (3.0.0.RELEASE). This
discrepancy was due to the fact that reactor-netty now brings in
reactor-core 3.0.0.RELEASE. Gradle's version conflict resolution is to use
the latest version. However, the optional dependency on reactor-core
3.0.0.BUILD-SNAPSHOT was making the build path of the IDE use the SNAPSHOT.

This fix leverages a resolutionStrategy to ensure a consistent version of
reactor-core is used throughout the entire project. It also bumps up the
reactor-core version to 3.0.0.RELEASE to be consistent with reactor-netty.
Care is taken to only change 3.x vesion since 2.x is still used within
the codebase.

spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework