Add velocity-backend-jdbi: the Postgres tumbling reference backend

settings.gradle.kts

@@ -58,7 +58,7 @@ include("velocity-api")      // OpenAPI 3.1 document + shared API DTOs (source o
 include("velocity-testkit")  // in-memory velocity-spi impl, conformance TCK scenarios, fixtures
 
 // Phase 2 — v1 reference backends (tumbling + sliding), the service tier, and the generated client.
-// include("velocity-backend-jdbi")   // Postgres/JDBI backend — v1 tumbling reference
+include("velocity-backend-jdbi")   // Postgres/JDBI backend — v1 tumbling reference
 // include("velocity-backend-redis")  // Redis/Lettuce backend — v1 sliding / hot-path reference
 // include("velocity-dropwizard")     // Dropwizard bundle, Jersey resources, Dagger wiring, API-key auth
 // include("velocity-client-java")    // Java client generated from OpenAPI via openapi-generator

velocity-backend-jdbi/build.gradle.kts

@@ -0,0 +1,49 @@
+plugins {
+    id("velocity.library-conventions")
+    id("velocity.test-conventions")
+    id("velocity.publish-conventions")
+}
+
+description =
+    "velocity-backend-jdbi: the v1 Postgres/JDBI tumbling reference backend — an exact, atomic," +
+        " read-your-write VelocityBackend (COUNT/SUM/DISTINCT over tumbling windows) that passes the" +
+        " velocity-testkit conformance TCK against real Postgres via Testcontainers."
+
+// JDBI, HikariCP, PostgreSQL and Testcontainers ship as automatic modules (no module-info); the
+// baseline -Xlint:all makes their `requires` a warning, which -Werror (library-conventions) turns
+// fatal. Mirror the pk-auth JDBI module and silence just the automatic-module lints on both the
+// main and test compiles.
+tasks.named<JavaCompile>("compileJava") {
+    options.compilerArgs.addAll(
+        listOf("-Xlint:-requires-automatic", "-Xlint:-requires-transitive-automatic"),
+    )
+}
+tasks.named<JavaCompile>("compileTestJava") {
+    options.compilerArgs.addAll(
+        listOf("-Xlint:-requires-automatic", "-Xlint:-requires-transitive-automatic"),
+    )
+}
+
+dependencies {
+    // The frozen contract this backend implements is on the api surface.
+    api(project(":velocity-spi"))
+    api(libs.jspecify)
+
+    implementation(libs.jdbi.core)
+    implementation(libs.postgresql)
+    implementation(libs.hikaricp)
+    implementation(libs.slf4j.api)
+
+    // JDBI's class files reference com.google.errorprone.annotations.concurrent.GuardedBy; without
+    // errorprone-annotations on the compile classpath javac emits an annotation-not-found warning
+    // that -Werror turns fatal. compileOnly so it is not broadcast as a runtime dependency.
+    compileOnly(libs.build.errorprone.annotations)
+    testCompileOnly(libs.build.errorprone.annotations)
+
+    // The testkit drives the conformance TCK (*Scenarios) + MutableClock against this backend.
+    testImplementation(project(":velocity-testkit"))
+    testImplementation(libs.testcontainers.core)
+    testImplementation(libs.testcontainers.junit.jupiter)
+    testImplementation(libs.testcontainers.postgresql)
+    testRuntimeOnly(libs.logback.classic)
+}