Bazel migration for Flink module (#237)

## Summary
Migrated `Flink` module to Bazel from sbt.

## Checklist
- [ ] Added Unit Tests
- [x] Covered by existing CI
- [ ] Integration tested
- [ ] Documentation update



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
	- Added Scala library definitions for the main application and testing.
- Introduced new Apache Flink dependencies for streaming, metrics, and
client interactions.

- **Chores**
- Updated build configuration to support a modular Scala project
structure.
	- Enhanced Maven repository with additional Flink-related libraries.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: kumar-zlai

flink/BUILD.bazel

@@ -0,0 +1,79 @@
+flink_deps = [
+    scala_artifact("org.apache.flink:flink-streaming-scala"),
+    scala_artifact("org.apache.flink:flink-scala"),
+    maven_artifact("org.apache.flink:flink-streaming-java"),
+    maven_artifact("org.apache.flink:flink-core"),
+    maven_artifact("org.apache.flink:flink-metrics-dropwizard"),
+    maven_artifact("org.apache.flink:flink-metrics-core"),
+    maven_artifact("org.apache.flink:flink-clients"),
+    maven_artifact("org.apache.flink:flink-yarn"),
+]
+
+flink_test_deps = [
+    # Libraries
+    scala_artifact("org.apache.flink:flink-streaming-scala"),
+    scala_artifact("org.apache.flink:flink-scala"),
+    maven_artifact("org.apache.flink:flink-streaming-java"),
+    maven_artifact("org.apache.flink:flink-core"),
+    maven_artifact("org.apache.flink:flink-runtime"),
+    # Testing
+    maven_artifact("org.apache.flink:flink-test-utils"),
+    maven_artifact("org.apache.flink:flink-runtime-tests"),
+]
+
+scala_library(
+    name = "lib",
+    srcs = glob(["src/main/**/*.scala"]),
+    visibility = ["//visibility:public"],
+    deps = flink_deps + [
+        "//api:lib",
+        "//api:thrift",
+        "//aggregator:lib",
+        "//online:lib",
+        "//tools/build_rules/spark:spark-exec",
+        scala_artifact("org.scala-lang.modules:scala-java8-compat"),
+        scala_artifact("org.scala-lang.modules:scala-collection-compat"),
+        scala_artifact("org.rogach:scallop"),
+        maven_artifact("io.dropwizard.metrics:metrics-core"),
+    ],
+)
+
+test_deps = flink_test_deps + [
+    ":lib",
+    "//online:lib",
+    "//api:thrift",
+    "//api:lib",
+    "//aggregator:lib",
+    "//tools/build_rules/spark:spark-exec",
+    # Libraries
+    scala_artifact("org.scala-lang.modules:scala-java8-compat"),
+    scala_artifact("org.scala-lang.modules:scala-collection-compat"),
+    # Testing
+    scala_artifact("org.scalatest:scalatest-matchers-core"),
+    scala_artifact("org.scalatest:scalatest-core"),
+    scala_artifact("org.scalatest:scalatest"),
+    scala_artifact("org.scalatest:scalatest-flatspec"),
+    scala_artifact("org.scalatest:scalatest-funsuite"),
+    scala_artifact("org.scalatest:scalatest-shouldmatchers"),
+    scala_artifact("org.scalactic:scalactic"),
+    scala_artifact("org.scalatestplus:mockito-3-4"),
+    scala_artifact("org.mockito:mockito-scala"),
+    maven_artifact("org.mockito:mockito-core"),
+    maven_artifact("org.scalatest:scalatest-compatible"),
+    maven_artifact("junit:junit"),
+    maven_artifact("com.novocode:junit-interface"),
+]
+
+scala_library(
+    name = "test-lib",
+    srcs = glob(["src/test/**/*.scala"]),
+    visibility = ["//visibility:public"],
+    deps = test_deps,
+)
+
+scala_test_suite(
+    name = "test",
+    srcs = glob(["src/test/**/*.scala"]),
+    visibility = ["//visibility:public"],
+    deps = test_deps + [":test-lib",],
+)

tools/build_rules/dependencies/maven_repository.bzl

@@ -57,6 +57,15 @@ maven_repository = repository(
         # Kafka
         "org.apache.kafka:kafka-clients:3.9.0",
 
+        # Flink
+        "org.apache.flink:flink-streaming-scala_2.12:1.17.0",
+        "org.apache.flink:flink-metrics-dropwizard:1.17.0",
+        "org.apache.flink:flink-clients:1.17.0",
+        "org.apache.flink:flink-yarn:1.17.0",
+        "org.apache.flink:flink-runtime:1.17.0",
+        "org.apache.flink:flink-runtime:1.17.0:tests",
+        "org.apache.flink:flink-test-utils:1.17.0",
+
         # Vertx
         "io.vertx:vertx-core:4.5.10",
         "io.vertx:vertx-web:4.5.10",