GelfHttpAppender does not set Uri

[formatq]

Describe the bug
GEtting error:
ERROR in de.siegmar.logbackgelf.GelfHttpAppender[GELF] - URI is required
even if uri field has correct uri like http://localhost:33002/gelf.

The field insecure is changed to true correctly.

To Reproduce
Try to use configuration like:

`

    <uri>http://localhost:33002/gelf</uri>
    <insecure>true</insecure>

    <encoder class="de.siegmar.logbackgelf.GelfEncoder">
        <includeRawMessage>false</includeRawMessage>
        <includeMarker>true</includeMarker>
        <includeMdcData>true</includeMdcData>
        <includeCallerData>false</includeCallerData>
        <includeRootCauseData>false</includeRootCauseData>
        <includeLevelName>true</includeLevelName>
        <appendNewline>true</appendNewline>
        <shortPatternLayout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%m%nopex</pattern>
        </shortPatternLayout>
        <fullPatternLayout class="ch.qos.logback.classic.PatternLayout">
            <pattern>%n</pattern>
        </fullPatternLayout>
    </encoder>
</appender>

`

Additional context

• Java distribution and version in use (output of java -version):
  17

• SLF4J and Logback version in use:
  1.5.3

• Some my investigation
  I did some debug and found that method ch.qos.logback.core.joran.util.AggregationAssessor#getDefaultClassNameByAnnonation tries to read DefaultClass annotation to pick correct Java Class for the path string, but looks like class GelfHttpAppender does not have it.

Sorry for messy report. Hope it's helps you some how.

[osiegmar]

Thanks for pointing out!