Modernize gradle build scripts

Includes:
- Translate Groovy DSL to Kotlin DSL
- Implement 'convention plugin' (see https://docs.gradle.org/current/userguide/sharing_build_logic_between_subprojects.html#sec:convention_plugins_vs_cross_configuration)
- Implement version catalog
- Upgrade to gradle 8.7
- Implement ktlint and correct code format problems
- Translate remaining Java files into Kotlin

.editorconfig

@@ -8,17 +8,23 @@ root = true
 # Change these settings to your own preference
 indent_style = space
 indent_size = 4
-continuation_indent_size = 8
+ij_continuation_indent_size = 8
 
 # We recommend you to keep these unchanged
 end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
+[{*.kt,*.kts}]
+ktlint_code_style = ktlint_official
+ij_kotlin_packages_to_use_import_on_demand = java.util.*
+
+[{*.java}]
+
 [*.ts]
 quote_type = single
-continuation_indent_size = 4
+ij_continuation_indent_size = 4
 
 [*.md]
 trim_trailing_whitespace = false

.gitignore

@@ -89,8 +89,8 @@ out/
 ######################
 # Gradle
 ######################
-.gradle/
-/build/
+.gradle
+build
 .gradletasknamecache
 
 ######################

Dockerfile

@@ -19,8 +19,9 @@ COPY .yarn /code/.yarn
 RUN yarn install --network-timeout 1000000
 
 COPY gradle gradle
-COPY gradlew build.gradle gradle.properties settings.gradle /code/
-COPY radar-auth/build.gradle radar-auth/
+COPY gradlew build.gradle.kts gradle.properties settings.gradle.kts /code/
+COPY radar-auth/build.gradle.kts radar-auth/
+COPY buildSrc/ buildSrc/
 
 RUN ./gradlew downloadDependencies
 
@@ -39,7 +40,7 @@ FROM eclipse-temurin:17-jre
 
 ENV SPRING_OUTPUT_ANSI_ENABLED=ALWAYS \
     JHIPSTER_SLEEP=0 \
-    JAVA_OPTS="" 
+    JAVA_OPTS=""
 
 # Add the war and changelogs files from build stage
 COPY --from=builder /code/build/libs/*.war /app.war