chore: Add missing javadocs in Consensus Service

[petreze]

Description:
This PR adds missing javadocs to Consensus Service

Related issue(s):

Fixes #15283

Notes for reviewer:

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -1.00%)	✅ ∅

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (60b03c5)	109328	67535	61.77%
Head commit (e428cd4)	109328 (+0)	67535 (+0)	61.77% (+0.00%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#15299)	0	0	∅ (not applicable)

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.23%. Comparing base (60b03c5) to head (e428cd4).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop   #15299   +/-   ##
==========================================
  Coverage      58.23%   58.23%           
  Complexity     21611    21611           
==========================================
  Files           2784     2784           
  Lines         109511   109511           
  Branches       11197    11197           
==========================================
  Hits           63773    63773           
  Misses         41866    41866           
  Partials        3872     3872           

Files with missing lines	Coverage Δ
...p/service/consensus/impl/ConsensusServiceImpl.java	100.00% <ø> (ø)
...app/service/consensus/impl/WritableTopicStore.java	100.00% <ø> (ø)
...sus/impl/handlers/ConsensusCreateTopicHandler.java	81.96% <ø> (ø)
...sus/impl/handlers/ConsensusDeleteTopicHandler.java	77.50% <ø> (ø)
...us/impl/handlers/ConsensusGetTopicInfoHandler.java	55.55% <ø> (ø)
...ice/consensus/impl/handlers/ConsensusHandlers.java	100.00% <ø> (ø)
...s/impl/handlers/ConsensusSubmitMessageHandler.java	92.85% <ø> (ø)
...sus/impl/handlers/ConsensusUpdateTopicHandler.java	65.44% <ø> (ø)
...e/consensus/impl/schemas/V0490ConsensusSchema.java	100.00% <ø> (ø)
...a/node/app/service/consensus/ConsensusService.java	33.33% <ø> (ø)
... and 1 more

[mhess-swl]

Are these comments required by one of the tools we use? Most of the added javadocs don't really add anything helpful, leading me to believe we're trying to appease Codacy (or some other linter) more than actually improving the code.

For example, indicating default injection over a constructor with // Dagger 2 or // Exists for injection:

    /**
     * Default constructor for injection.
     */
    @Inject
    public ConsensusUpdateTopicHandler() {
        // Exists for injection

The javadoc is just three extra lines that duplicates the existing comment.

Another example is re-wording a file/class name into a sentence form:

/**
 * Unit tests of Consensus Service
 */
public class ConsensusServiceImplTest {

or

/**
 * Util class used in unit tests for Consensus Service
 */
public final class ConsensusTestUtils {

As a general rule, if a javadoc doesn't add any extra information, personally I would prefer not to have the javadoc at all. It's redundant reading. What are your thoughts, though? Are there advantages I'm not thinking about?

[petreze]

@mhess-swl
There is built in tool inside the IDE that scans for missing javadocs. I agree that some of those suggestions are quite useless or not that much of a win but I see that there are similar javadocs in other services after this refactoring

[tinker-michaelj]

LGTM, tyvm @petreze !