Mailetdoc throws a lot of exceptions about missing method(constructor) or classes during tests

When running tests (`mvn test`), Maildoc reporter throws a lot of exceptions, either `NoSuchMethodException` or `ClassNotFoundException`. Quote from the mail:

>> And the full build
>> (https://ci-builds.apache.org/job/james/job/ApacheJames/job/PR-1476/9/console) has other issues, for example lots of NoSuchMethodException from `MailetdocsReport.buildDescriptors (MailetdocsReport.java:49)` (those are quite probably caused by switch to injection-by-constructor and lack of default constructor) or ClassNotFoundException (not sure about those, classpath/lack of dependency) but then the whole Mailetdocs Report fails in a lot of cases (~1,6k exceptions from total of ~8k)
> +1 to open a ticket and address that one.
>
> Likely a easy fix inside the mailetdoc plugin....

Relevant stactraces for both cases:

```
19:48:37,365 [INFO] — git-commit-id-plugin:4.9.10:revision (get-the-git-infos) @ apache-james-mailbox-tools-quota-recompute —
19:48:37,440 [INFO] Cannot load mailet info for org.apache.james.jdkim.mailets.DKIMVerify
java.lang.NoSuchMethodException: org.apache.james.jdkim.mailets.DKIMVerify.<init>()
at java.lang.Class.getConstructor0 (Class.java:3349)
at java.lang.Class.getDeclaredConstructor (Class.java:2553)
at org.apache.james.mailet.DefaultDescriptorsExtractor.fetchInfo (DefaultDescriptorsExtractor.java:174)
at org.apache.james.mailet.DefaultDescriptorsExtractor.describeMailet (DefaultDescriptorsExtractor.java:217)
at org.apache.james.mailet.DefaultDescriptorsExtractor.addDescriptor (DefaultDescriptorsExtractor.java:116)
at org.apache.james.mailet.DefaultDescriptorsExtractor.extract (DefaultDescriptorsExtractor.java:83)
at org.apache.james.mailet.MailetdocsReport.buildDescriptors (MailetdocsReport.java:49)
at org.apache.james.mailet.AbstractMailetdocsReport.buildSortedDescriptors (AbstractMailetdocsReport.java:132)
at org.apache.james.mailet.AbstractMailetdocsReport.writeDescriptions (AbstractMailetdocsReport.java:89)
at org.apache.james.mailet.AbstractMailetdocsReport.executeReport (AbstractMailetdocsReport.java:79)
at org.apache.maven.reporting.AbstractMavenReport.generate (AbstractMavenReport.java:237)
at org.apache.maven.reporting.AbstractMavenReport.execute (AbstractMavenReport.java:143)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
```

and
```
19:48:41,871 [ERROR] NotFound
java.lang.ClassNotFoundException: org.apache.james.transport.mailets.model.ICALAttributeDTO.Builder
at java.net.URLClassLoader.findClass (URLClassLoader.java:476)
at java.lang.ClassLoader.loadClass (ClassLoader.java:589)
at java.lang.ClassLoader.loadClass (ClassLoader.java:522)
at org.apache.james.mailet.DefaultDescriptorsExtractor.addDescriptor (DefaultDescriptorsExtractor.java:109)
at org.apache.james.mailet.DefaultDescriptorsExtractor.extract (DefaultDescriptorsExtractor.java:83)
at org.apache.james.mailet.MailetdocsReport.buildDescriptors (MailetdocsReport.java:49)
at org.apache.james.mailet.AbstractMailetdocsReport.buildSortedDescriptors (AbstractMailetdocsReport.java:132)
at org.apache.james.mailet.AbstractMailetdocsReport.writeDescriptions (AbstractMailetdocsReport.java:89)
at org.apache.james.mailet.AbstractMailetdocsReport.executeReport (AbstractMailetdocsReport.java:79)
at org.apache.maven.reporting.AbstractMavenReport.generate (AbstractMavenReport.java:237)
at org.apache.maven.reporting.AbstractMavenReport.execute (AbstractMavenReport.java:143)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
```