Warn users of old Java version 18 months before end of life (#8543)

core/src/main/java/jenkins/monitor/JavaVersionRecommendationAdminMonitor.java

@@ -115,7 +115,7 @@ private static String getId() {
 
     @Override
     public boolean isActivated() {
-        return !disabled && getDeprecationPeriod().getYears() < 2;
+        return !disabled && getDeprecationPeriod().toTotalMonths() < 18;
     }
 
     @Override
@@ -156,7 +156,7 @@ private static Period getDeprecationPeriod() {
 
     @NonNull
     private static Severity getSeverity() {
-        return getDeprecationPeriod().getYears() < 1 ? Severity.DANGER : Severity.WARNING;
+        return getDeprecationPeriod().toTotalMonths() < 9 ? Severity.DANGER : Severity.WARNING;
     }
 
     /**

core/src/main/resources/jenkins/monitor/JavaVersionRecommendationAdminMonitor/description.jelly

@@ -1,4 +1,4 @@
 <?jelly escape-by-default='true'?>
 <j:jelly xmlns:j="jelly:core" xmlns:l="/lib/layout" xmlns:f="/lib/form" xmlns:i="jelly:fmt" xmlns:st="jelly:stapler">
-    ${%blurb(it.javaVersion)}
+    ${%blurb}
 </j:jelly>

core/src/main/resources/jenkins/monitor/JavaVersionRecommendationAdminMonitor/description.properties

@@ -1 +1 @@
-blurb = Recommends Java {0,number} for running Jenkins if an older version is used.
+blurb = Recommends a Java upgrade for Jenkins if an older Java version is used.

core/src/main/resources/jenkins/monitor/JavaVersionRecommendationAdminMonitor/description_pt_BR.properties

@@ -20,4 +20,4 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
-blurb=Recomenda o Java {0,number} para executar o Jenkins se uma versão anterior está em uso.
+blurb=Recomenda uma atualização do Java para Jenkins se uma versão anterior do Java estiver em uso.

core/src/main/resources/jenkins/monitor/JavaVersionRecommendationAdminMonitor/description_ru.properties

@@ -1 +1 @@
-blurb = Рекомендует запускать Jenkins на Java {0,number}, если используется более старая версия.
+blurb = Рекомендует обновить Java для Jenkins, если используется более старая версия Java.

core/src/main/resources/jenkins/monitor/JavaVersionRecommendationAdminMonitor/description_zh_TW.properties

@@ -1 +1 @@
-blurb=若您使用的 Java 版本低於 {0,number}，推薦您改用 Java {0,number} 來執行 Jenkins。
+blurb=如果使用較舊的 Java 版本，建議對 Jenkins 進行 Java 升級。