[context] Prevent unintended usage of JDK 21 feature (closes #2117)

- import kotlin.collections.removeFirst as removeFirstKt
- Set <release> instead of <source> and <target>
- Downgrade JTE to 2x

.github/workflows/publish-snapshots.yml

@@ -9,8 +9,6 @@ jobs:
     if: |
       github.repository == 'javalin/javalin' &&
       !contains(github.event.head_commit.message, '[maven-release-plugin] prepare release')
-      
-
     name: Publish snapshot
     runs-on: ubuntu-latest
     steps:
@@ -19,7 +17,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
           distribution: 'zulu'
-          java-version: 21
+          java-version: 11
       - name: Grant execute permission for mvnw
         run: chmod +x ./mvnw
       - uses: s4u/maven-settings-action@v3.0.0

javalin-rendering/pom.xml

@@ -12,7 +12,7 @@
 
     <properties>
         <copy-build-resources.skip>false</copy-build-resources.skip>
-        <jte.version>3.0.2</jte.version>
+        <jte.version>2.3.2</jte.version>
     </properties>
 
     <dependencies>

javalin/src/main/java/io/javalin/http/Cookie.kt

@@ -3,6 +3,7 @@ package io.javalin.http
 import jakarta.servlet.http.HttpServletRequest
 import jakarta.servlet.http.HttpServletResponse
 import jakarta.servlet.http.Cookie as ServletCookie
+import kotlin.collections.removeFirst as removeFirstKt
 
 const val SAME_SITE = "SameSite"
 
@@ -86,7 +87,7 @@ fun HttpServletResponse.setJavalinCookie(javalinCookie: Cookie) {
     this.addCookie(cookie) // we rely on this method for formatting the cookie header
     (this.getHeaders(Header.SET_COOKIE) ?: listOf()).toMutableList().let { cookies -> // mutable list of all cookies
         cookies.removeIf { it.startsWith("${cookie.name}=") && !it.contains(cookie.value) } // remove old cookie if duplicate name
-        cookies.removeFirst()?.let { first -> this.setHeader(Header.SET_COOKIE, first.addSameSite(javalinCookie)) } // remove first cookie and use it to clear the header
+        cookies.removeFirstKt()?.let { first -> this.setHeader(Header.SET_COOKIE, first.addSameSite(javalinCookie)) } // remove first cookie and use it to clear the header
         cookies.forEach { remaining -> this.addHeader(Header.SET_COOKIE, remaining.addSameSite(javalinCookie)) } // add all remaining cookies
     }
 

pom.xml

@@ -303,8 +303,7 @@
                     </execution>
                 </executions>
                 <configuration>
-                    <source>${jdk.version}</source>
-                    <target>${jdk.version}</target>
+                    <release>${jdk.version}</release>
                 </configuration>
             </plugin>
             <plugin>