Add Kotlin usage meter with Postgres quotas and ClickPipes reports

.github/workflows/usage-meter.yml

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+name: Usage meter checks
+on:
+  pull_request:
+    paths: ['applications/usage-meter/**', '.github/workflows/usage-meter.yml']
+  push:
+    branches: [main]
+    paths: ['applications/usage-meter/**', '.github/workflows/usage-meter.yml']
+  workflow_dispatch:
+permissions:
+  contents: read
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: applications/usage-meter
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '21'
+      - run: ./gradlew --no-daemon clean test installDist
+# Real Cloud acceptance is explicit and does not use CI credentials.

applications/usage-meter/.env.example

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+PGHOST=YOUR_DIRECT_CLOUD_POSTGRES_HOSTNAME
+PGPORT=5432
+PGDATABASE=postgres
+PGUSER=usage_app
+PGPASSWORD=YOUR_RUNTIME_PASSWORD
+PGSSLROOTCERT=/absolute/path/to/postgres-ca.pem
+CLICKHOUSE_URL=https://YOUR_CLICKHOUSE_HOSTNAME:8443
+CLICKHOUSE_USER=usage_reports
+CLICKHOUSE_PASSWORD=YOUR_REPORT_PASSWORD
+ACCOUNT_TOKENS='{"00000000-0000-4000-8000-000000000001":"YOUR_RANDOM_TOKEN_AT_LEAST_32_CHARACTERS","00000000-0000-4000-8000-000000000002":"ANOTHER_RANDOM_TOKEN_AT_LEAST_32_CHARACTERS"}'
+PORT=3000
+# Tests only: RUN_CLOUD_TESTS=1 and TEST_WRONG_CA=/absolute/path/to/unrelated-ca.pem
+# Keep migration, publication/CDC and administrator passwords out of this file.

applications/usage-meter/.gitattributes

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+gradlew.bat text eol=crlf

applications/usage-meter/.gitignore

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+.gradle/
+build/
+.deployment/
+.env
+*.log

applications/usage-meter/build.gradle.kts

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+plugins {
+    kotlin("jvm") version "2.4.20"
+    kotlin("plugin.serialization") version "2.4.20"
+    application
+}
+repositories { mavenCentral() }
+kotlin { jvmToolchain(21) }
+application { mainClass.set("meter.MainKt") }
+dependencyLocking { lockAllConfigurations() }
+dependencies {
+    val ktor = "3.6.0"
+    implementation("io.ktor:ktor-server-netty-jvm:$ktor")
+    implementation("io.ktor:ktor-server-auth-jvm:$ktor")
+    implementation("io.ktor:ktor-server-content-negotiation-jvm:$ktor")
+    implementation("io.ktor:ktor-server-status-pages-jvm:$ktor")
+    implementation("io.ktor:ktor-server-body-limit-jvm:$ktor")
+    implementation("io.ktor:ktor-serialization-kotlinx-json-jvm:$ktor")
+    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.11.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.11.0")
+    implementation("org.jetbrains.exposed:exposed-core:1.5.0")
+    implementation("org.jetbrains.exposed:exposed-jdbc:1.5.0")
+    implementation("org.jetbrains.exposed:exposed-java-time:1.5.0")
+    implementation("org.postgresql:postgresql:42.7.13")
+    implementation("com.zaxxer:HikariCP:7.1.0")
+    implementation("com.clickhouse:client-v2:0.10.0")
+    implementation("ch.qos.logback:logback-classic:1.6.5")
+    testImplementation(kotlin("test-junit5"))
+    testImplementation("org.junit.jupiter:junit-jupiter:6.0.3")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher:6.0.3")
+}
+tasks.test { useJUnitPlatform() }

applications/usage-meter/gradle.properties

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+org.gradle.jvmargs=-Xmx768m -Dfile.encoding=UTF-8
+org.gradle.workers.max=1
+kotlin.compiler.execution.strategy=in-process

applications/usage-meter/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionSha256Sum=bafd5ce9cfaea0fbccfdc8439a1ac42fbd4cd9c89dc9a988228d8a2639a58e6c
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.8.0-bin.zip
+networkTimeout=30000
+retries=2
+retryBackOffMs=500
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists