Generalize OTEL API and add memcache tracing support

- Rename RedisSpan -> SpanHandle for generic span handling
- Generalize TelemetryController methods: startSpan/endSpan with dbSystem param
- Rename RedisOtelSpan -> OtelSpanHandle in rbcs-server-otel
- Update Redis cache handler to use new generic API
- Add OpenTelemetry tracing for memcache GET and SET commands
- Add channel property to MemcacheRequestController for server address attribution
- Add uses TelemetryController directive in memcache module-info

Memcache spans follow the same pattern as Redis:
db.system=memcache, db.operation=GET|SET, server.address, server.port

rbcs-server-otel/src/main/kotlin/net/woggioni/rbcs/server/otel/OtelController.kt

@@ -2,13 +2,14 @@ package net.woggioni.rbcs.server.otel
 
 import io.netty.channel.ChannelHandler
 import io.opentelemetry.api.GlobalOpenTelemetry
+import io.opentelemetry.api.common.AttributeKey
 import io.opentelemetry.api.trace.SpanKind
 import io.opentelemetry.api.trace.StatusCode
 import io.opentelemetry.instrumentation.logback.appender.v1_0.OpenTelemetryAppender
 import io.opentelemetry.instrumentation.netty.v4_1.NettyServerTelemetry
 import io.opentelemetry.instrumentation.runtimetelemetry.RuntimeTelemetry
 import io.opentelemetry.sdk.autoconfigure.AutoConfiguredOpenTelemetrySdk
-import net.woggioni.rbcs.api.RedisSpan
+import net.woggioni.rbcs.api.SpanHandle
 import net.woggioni.rbcs.api.TelemetryController
 import net.woggioni.rbcs.common.createLogger
 import net.woggioni.rbcs.common.info
@@ -44,21 +45,19 @@ class OtelController : TelemetryController {
         return NettyServerTelemetry.create(GlobalOpenTelemetry.get()).createCombinedHandler()
     }
 
-    override fun startRedisSpan(command: String, key: String): RedisSpan? {
-        val span = tracer.spanBuilder(command)
+    override fun startSpan(name: String): SpanHandle {
+        val span = tracer.spanBuilder(name)
             .setSpanKind(SpanKind.CLIENT)
-            .setAttribute("db.system", "redis")
-            .setAttribute("db.operation", command)
             .startSpan()
-        return RedisOtelSpan(span)
+        return OtelSpanHandle(span)
     }
 
-    override fun endRedisSpan(span: RedisSpan?) {
-        (span as? RedisOtelSpan)?.delegate?.end()
+    override fun endSpan(span: SpanHandle?) {
+        (span as? OtelSpanHandle)?.delegate?.end()
     }
 
-    override fun endRedisSpan(span: RedisSpan?, error: Throwable) {
-        val s = (span as? RedisOtelSpan)?.delegate ?: return
+    override fun endSpan(span: SpanHandle?, error: Throwable) {
+        val s = (span as? OtelSpanHandle)?.delegate ?: return
         s.recordException(error)
         s.setStatus(StatusCode.ERROR)
         s.end()

rbcs-server-otel/src/main/kotlin/net/woggioni/rbcs/server/otel/OtelSpanHandle.kt

@@ -1,11 +1,11 @@
 package net.woggioni.rbcs.server.otel
 
 import io.opentelemetry.api.trace.Span
-import net.woggioni.rbcs.api.RedisSpan
+import net.woggioni.rbcs.api.SpanHandle
 
-internal class RedisOtelSpan(
+internal class OtelSpanHandle(
     val delegate: Span,
-) : RedisSpan {
+) : SpanHandle {
 
     override fun setAttribute(key: String, value: String) {
         delegate.setAttribute(key, value)
@@ -14,4 +14,8 @@ internal class RedisOtelSpan(
     override fun setAttribute(key: String, value: Long) {
         delegate.setAttribute(key, value)
     }
+
+    override fun setAttribute(key: String, value: Boolean) {
+        delegate.setAttribute(key, value)
+    }
 }