Reduce duplicate configuration details

Adapters must now declare a `spigot.version` property.

* Greatly simplifies and speeds up retrieval of Spigot versions

pom.xml

@@ -1,5 +1,5 @@
 <!--
-  ~ Copyright (C) 2011-2021 lishid. All rights reserved.
+  ~ Copyright (C) 2011-2022 lishid. All rights reserved.
   ~
   ~ This program is free software: you can redistribute it and/or modify
   ~ it under the terms of the GNU General Public License as published by
@@ -29,6 +29,8 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <maven.compiler.source>1.8</maven.compiler.source>
     <maven.compiler.target>1.8</maven.compiler.target>
+    <!-- Silence IDE warning - property is declared in individual internal modules. -->
+    <spigot.version>unknown</spigot.version>
   </properties>
 
   <profiles>
@@ -144,6 +146,34 @@
           <groupId>net.md-5</groupId>
           <artifactId>specialsource-maven-plugin</artifactId>
           <version>1.2.2</version>
+          <executions>
+            <execution>
+              <phase>package</phase>
+              <goals>
+                <goal>remap</goal>
+              </goals>
+              <id>remap-obf</id>
+              <configuration>
+                <srgIn>org.spigotmc:minecraft-server:${spigot.version}:txt:maps-mojang</srgIn>
+                <reverse>true</reverse>
+                <remappedDependencies>org.spigotmc:spigot:${spigot.version}:jar:remapped-mojang</remappedDependencies>
+                <remappedArtifactAttached>true</remappedArtifactAttached>
+                <remappedClassifierName>remapped-obf</remappedClassifierName>
+              </configuration>
+            </execution>
+            <execution>
+              <phase>package</phase>
+              <goals>
+                <goal>remap</goal>
+              </goals>
+              <id>remap-spigot</id>
+              <configuration>
+                <inputFile>${project.build.directory}/${project.artifactId}-${project.version}-remapped-obf.jar</inputFile>
+                <srgIn>org.spigotmc:minecraft-server:${spigot.version}:csrg:maps-spigot</srgIn>
+                <remappedDependencies>org.spigotmc:spigot:${spigot.version}:jar:remapped-obf</remappedDependencies>
+              </configuration>
+            </execution>
+          </executions>
         </plugin>
       </plugins>
     </pluginManagement>