[FLINK-15899] [build] Inherit from Apache Parent POM

[tzulitai]

This is a first step towards making Stateful Functions release-ready.

See details about what settings the Apache Parent POM covers here: https://maven.apache.org/pom/asf/index.html.

As an end result of this change, we should be able to perform mvn clean install -Papache-release without issues.

[tzulitai]

Building with mvn clean install -Papache-release currently fails with the following:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-javadoc-plugin:3.0.1:jar (attach-javadocs) on project statefun-sdk: MavenReportException: Error while generating Javadoc:
[ERROR] Exit code: 1 - /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/Context.java:70: error: bad use of '>'
[ERROR]    * @param delay the amount of delay before invoking the target function. Value needs to be >= 0.
[ERROR]                                                                                              ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/Context.java:92: error: bad use of '>'
[ERROR]    * @param delay the amount of delay before invoking the target function. Value needs to be >= 0.
[ERROR]                                                                                              ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/StatefulFunction.java:54: error: unterminated inline tag
[ERROR]  * <pre>{@code
[ERROR]         ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/StatefulFunction.java:57: error: unknown tag: Persisted
[ERROR]  *     @Persisted
[ERROR]        ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/StatefulFunction.java:58: error: unknown tag: Integer
[ERROR]  *     PersistedValue<Integer> intState = PersistedValue.of("state-name", Integer.class);
[ERROR]                      ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/StatefulFunction.java:60: error: unknown tag: Override
[ERROR]  *     @Override
[ERROR]        ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/match/MatchBinder.java:70: warning: no @return
[ERROR]   public <T> MatchBinder predicate(Class<T> type, BiConsumer<Context, T> action) {
[ERROR]                          ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/match/MatchBinder.java:96: warning: no @return
[ERROR]   public <T> MatchBinder predicate(
[ERROR]                          ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/match/MatchBinder.java:113: warning: no @return
[ERROR]   public MatchBinder otherwise(BiConsumer<Context, Object> action) {
[ERROR]                      ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/spi/StatefulFunctionModule.java:55: error: malformed HTML
[ERROR]  * <ahref="https://github.com/google/auto/tree/master/service">AutoService</a> tool.
[ERROR]    ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/spi/StatefulFunctionModule.java:55: error: bad use of '>'
[ERROR]  * <ahref="https://github.com/google/auto/tree/master/service">AutoService</a> tool.
[ERROR]                                                               ^
[ERROR] /Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/spi/StatefulFunctionModule.java:55: error: unexpected end tag: </a>
[ERROR]  * <ahref="https://github.com/google/auto/tree/master/service">AutoService</a> tool.
[ERROR]                                                                           ^
[ERROR]
[ERROR] Command line was: /Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents/Home/jre/../bin/javadoc @options @packages
[ERROR]
[ERROR] Refer to the generated Javadoc files in '/Users/tzulitai/repos/apache/flink-statefun/statefun-sdk/target/apidocs' dir.

Will need to go through and fix the above Javadocs and maybe cover Javadoc checks in our builds.

[tzulitai]

The Javadocs are fixed with 45be13e.
You should be able to verify the changes now with mvn clean install -Papache-release.

We might at some point want to use the Maven Checkstyle Plugin to enforce checks on Javadocs per build.

cc @igalshilman

[igalshilman]

Thanks @tzulitai !
Can you check if spotless can be configured to conform with that java doc style?

[tzulitai]

Hi @igalshilman, I think it'll be possible, since Spotless is capable of formatting Javadocs.
I've filed a JIRA for this as a follow-up: https://issues.apache.org/jira/browse/FLINK-15930.

I'll proceed to merge this PR as is, thanks for the review.