[CI/CD]Add unit test

follow the root issue: #1460 Notice:

• The ut coverage is required to reach 60%
• UT only use junit and mockito, we worried about license issues after other library is introduced
• UT cannot include performance testing operations, blocking operations (time-consuming), and cannot rely on third-party libs. If you want to rely on testing, you can use mockito to mock.

The directory listing which will write ut is as following(if you want to contribute, you may reply "java.org.apache.dolphinscheduler.api.utils, i want to implement it, avoid everyone writing UT repeatedly):

├── java
│   └── org
│       └── apache
│           └── dolphinscheduler
│               └── api
│                   ├── ApiApplicationServer.java
│                   ├── CombinedApplicationServer.java
│                   ├── configuration
│                   ├── controller
│                   ├── dto
│                   ├── enums
│                   ├── interceptor
│                   ├── log
│                   ├── service
│                   └── utils

├── java
│   └── org
│       └── apache
│           └── dolphinscheduler
│               └── common
│                   ├── Constants.java
│                   ├── IStoppable.java
│                   ├── enums
│                   ├── graph
│                   ├── job
│                   ├── model
│                   ├── process
│                   ├── queue
│                   ├── shell
│                   ├── task
│                   ├── thread
│                   ├── utils
│                   └── zk

├── java
│   └── org
│       └── apache
│           └── dolphinscheduler
│               └── alert
│                   ├── AlertServer.java
│                   ├── manager
│                   ├── runner
│                   └── utils

If you had finished the ut, you should modify the pom.xml file, and add the include files like this:

			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-surefire-plugin</artifactId>
				<version>${maven-surefire-plugin.version}</version>
				<configuration>
					<includes>
						<include>**/common/graph/*.java</include><!--run test classes-->
					</includes>
					<!-- <skip>true</skip> -->
				</configuration>
			</plugin>

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Note: Now, ci has support db, if you develop mapper/dao ut, you can use it, and it had config in dolphinscheduler-dao/src/main/resources/application-dao.properties

[samz406]

I want to implements org.apache.dolphinscheduler.api.service.SessionService org.apache.dolphinscheduler.api.service.UsersService org.apache.dolphinscheduler.api.service.TenantService org.apache.dolphinscheduler.api.service.WorkerGroupService org.apache.dolphinscheduler.api.service.UdfFuncService org.apache.dolphinscheduler.api.service.AlertGroupService org.apache.dolphinscheduler.api.service.ProjectService

[nauu]

I found there is a shell UT in “implement org.apache.dolphinscheduler.common.shell”.

So I’d like to implement org.apache.dolphinscheduler.alert.utils