fix: update maven deploy workflow to upload to central (as ossrh is retired)

[akafredperry]

- What I did
Fixed the github action in at_java so that a SNAPSHOT of the latest version is now published to central portal snapshots. ossrh is now retired.
The artifact now has groupId of org.atsign
The initial version is 0.0.1-SNAPSHOT

fixes #287

- How I did it
Cleaned up the pom.xml as per the maven central guidelines
Adjusted the maven deploy-workflow.yml so that central server is created in settings.xml and credentials for central are used
Removed the redundant install mvn goal (deploy will install)

- How to verify it
Create a simple project java project and verify that you can resolve the dependencies, for example this pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>untitled</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <maven.compiler.source>18</maven.compiler.source>
    <maven.compiler.target>18</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <repositories>
    <repository>
      <name>Central Portal Snapshots</name>
      <id>central-portal-snapshots</id>
      <url>https://central.sonatype.com/repository/maven-snapshots</url>
      <releases>
        <enabled>false</enabled>
      </releases>
      <snapshots>
        <enabled>true</enabled>
      </snapshots>
    </repository>
  </repositories>

  <dependencies>
    <dependency>
      <groupId>org.atsign</groupId>
      <artifactId>at_client</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>
  </dependencies>
</project>

this command

mvn compile

should succeed and you should see this...

[INFO] Building untitled 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
Downloading from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/maven-metadata.xml
Downloaded from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/maven-metadata.xml (2.0 kB at 1.6 kB/s)
Downloading from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/at_client-0.0.1-20260127.155743-7.pom
Downloaded from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/at_client-0.0.1-20260127.155743-7.pom (7.2 kB at 8.3 kB/s)
Downloading from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/at_client-0.0.1-20260127.155743-7.jar
Downloaded from central-portal-snapshots: https://central.sonatype.com/repository/maven-snapshots/org/atsign/at_client/0.0.1-SNAPSHOT/at_client-0.0.1-20260127.155743-7.jar (163 kB at 109 kB/s)

- Description for the changelog

fixes artifact publish for at_client

[JeremyTubongbanua]

We like to do conventional commits for commits and PR titles

https://www.conventionalcommits.org/en/v1.0.0/#summary

[JeremyTubongbanua]

LGTM

Thanks for your work in this @akafredperry

[JeremyTubongbanua]

These were debug statements I added years ago and can be removed if you would like.