First sentence of Javadoc is not checked past default period character when using custom period

[patchwork01]

I have read check documentation: https://checkstyle.org/checks/javadoc/summaryjavadoc.html
I have downloaded the latest checkstyle from: https://checkstyle.org/cmdline.html#Download_and_Run
I have executed the cli and showed it below, as cli describes the problem better than 1,000 words

/var/tmp $ javac TestCheckstyleJavadocSummary.java

/var/tmp $ cat config.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC
        "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
        "https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
    <module name="TreeWalker">
        <module name="SummaryJavadoc">
            <property name="period" value="_"/>
            <property name="forbiddenSummaryFragments" value="forbidden-fragment"/>
        </module>
    </module>
</module>

/var/tmp $ cat TestCheckstyleJavadocSummary.java
public class TestCheckstyleJavadocSummary {

    /**
     * Summary sentence that happens to have a default period. in it, then forbidden-fragment, but the custom period is used_
     */
    void foo1() {
    }
}

/var/tmp $ RUN_LOCALE="-Duser.language=en -Duser.country=US"

/var/tmp $ java $RUN_LOCALE -jar checkstyle-10.14.2-all.jar -c config.xml TestCheckstyleJavadocSummary.java
Starting audit...
Audit done.

---

This should fail as the summary sentence contains "forbidden-fragment". It only fails if "forbidden-fragment" occurs before the default period character ".".

---

This bug was found while addressing the following issue:

• False positives when first sentence of Javadoc is on a separate line #14689

While fixing that, I also fixed this.

[romani]

willl be fixed in scope of fix for #14689