How to import Tomcat source code into idea

<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.apache.tomcat</groupId>
  <artifactId>tomcat</artifactId>
  <name>tomcat</name>
  <version>9.0.19</version>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.apache.ant</groupId>
      <artifactId>ant</artifactId>
      <version>1.10.11</version>
    </dependency>
    <dependency>
      <groupId>wsdl4j</groupId>
      <artifactId>wsdl4j</artifactId>
      <version>1.6.3</version>
    </dependency>

    <!-- https://mvnrepository.com/artifact/javax.xml.soap/javax.xml.soap-api -->
    <dependency>
      <groupId>javax.xml.soap</groupId>
      <artifactId>javax.xml.soap-api</artifactId>
      <version>1.4.0</version>
    </dependency>

    <dependency>
      <groupId>org.apache.geronimo.specs</groupId>
      <artifactId>geronimo-jaxrpc_1.1_spec</artifactId>
      <version>2.1</version>
    </dependency>

    <dependency>
      <groupId>org.eclipse.jdt</groupId>
      <artifactId>ecj</artifactId>
      <version>3.17.0</version>
    </dependency>


    <dependency>
      <groupId>org.easymock</groupId>
      <artifactId>easymock</artifactId>
      <version>4.0.2</version>
      <scope>test</scope>
    </dependency>

    <dependency>
      <groupId>biz.aQute.bnd</groupId>
      <artifactId>biz.aQute.bndlib</artifactId>
      <version>5.2.0</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>com.unboundid</groupId>
      <artifactId>unboundid-ldapsdk</artifactId>
      <version>3.2.0</version>
    </dependency>
  </dependencies>

</project>

Add a line of code to the org.apache.catalina.startup.ContextConfig#configureStart method //TODO manually added context.addServletContainerInitializer(new JasperInitializer(), null);