chore: add some comment about naming convention

ingester-protocol/src/main/java/io/greptime/models/Column.java

@@ -29,6 +29,13 @@
 @Target(ElementType.FIELD)
 public @interface Column {
 
+    /**
+     * The name of the column in the table.
+     * <p>
+     * It is strongly recommended to use snake case naming convention and avoid
+     * using camel case. This is because GreptimeDB treats column names as
+     * case-insensitive, which can cause confusion when querying with camel case.
+     */
     String name();
 
     boolean tag() default false;

ingester-protocol/src/main/java/io/greptime/models/TableSchema.java

@@ -77,6 +77,10 @@ public Builder(String tableName) {
 
         /**
          * Add tag schema.
+         * <p>
+         * It is strongly recommended to use snake case naming convention and avoid
+         * using camel case. This is because GreptimeDB treats column names as
+         * case-insensitive, which can cause confusion when querying with camel case.
          *
          * @param name the name of this tag
          * @param dataType the data type of this tag
@@ -88,6 +92,10 @@ public Builder addTag(String name, DataType dataType) {
 
         /**
          * Add timestamp schema.
+         * <p>
+         * It is strongly recommended to use snake case naming convention and avoid
+         * using camel case. This is because GreptimeDB treats column names as
+         * case-insensitive, which can cause confusion when querying with camel case.
          *
          * @param name the name of this timestamp
          * @param dataType the data type of this timestamp
@@ -101,6 +109,10 @@ public Builder addTimestamp(String name, DataType dataType) {
 
         /**
          * Add field schema.
+         * <p>
+         * It is strongly recommended to use snake case naming convention and avoid
+         * using camel case. This is because GreptimeDB treats column names as
+         * case-insensitive, which can cause confusion when querying with camel case.
          *
          * @param name the name of this field
          * @param dataType the data type of this field
@@ -112,6 +124,10 @@ public Builder addField(String name, DataType dataType) {
 
         /**
          * Add column schema.
+         * <p>
+         * It is strongly recommended to use snake case naming convention and avoid
+         * using camel case. This is because GreptimeDB treats column names as
+         * case-insensitive, which can cause confusion when querying with camel case.
          *
          * @param name the name of this column
          * @param semanticType the semantic type of this column (`Tag`, `Field` or `Timestamp`)
@@ -124,6 +140,10 @@ public Builder addColumn(String name, SemanticType semanticType, DataType dataTy
 
         /**
          * Add column schema.
+         * <p>
+         * It is strongly recommended to use snake case naming convention and avoid
+         * using camel case. This is because GreptimeDB treats column names as
+         * case-insensitive, which can cause confusion when querying with camel case.
          *
          * @param name the name of this column
          * @param semanticType the semantic type of this column (`Tag`, `Field` or `Timestamp`)
@@ -144,7 +164,7 @@ public Builder addColumn(String name, //
                         "Invalid timestamp data type: %s, only support `DataType.TimestampXXX`", dataType);
             }
 
-            // trim leading and trailing spaces
+            // Trim leading and trailing spaces
             name = name.trim();
 
             this.columnNames.add(name);

ingester-protocol/src/test/java/io/greptime/options/GreptimeOptionsTest.java

@@ -20,6 +20,7 @@
 import io.greptime.limit.LimitedPolicy;
 import io.greptime.models.AuthInfo;
 import io.greptime.rpc.RpcOptions;
+import io.greptime.rpc.TlsOptions;
 import org.junit.Assert;
 import org.junit.Test;
 import java.util.List;
@@ -44,10 +45,12 @@ public void testAllOptions() {
         long routeTableRefreshPeriodSeconds = 99;
         AuthInfo authInfo = new AuthInfo("user", "password");
         Router<Void, Endpoint> router = createTestRouter();
+        TlsOptions tlsOptions = new TlsOptions();
 
         GreptimeOptions opts = GreptimeOptions.newBuilder(endpoints, database) //
                 .asyncPool(asyncPool) //
                 .rpcOptions(rpcOptions) //
+                .tlsOptions(tlsOptions) //
                 .writeMaxRetries(writeMaxRetries) //
                 .maxInFlightWritePoints(maxInFlightWritePoints) //
                 .writeLimitedPolicy(limitedPolicy) //
@@ -60,6 +63,7 @@ public void testAllOptions() {
         Assert.assertEquals(database, opts.getDatabase());
         Assert.assertArrayEquals(endpoints, opts.getEndpoints().stream().map(Endpoint::toString).toArray());
         Assert.assertEquals(rpcOptions, opts.getRpcOptions());
+        Assert.assertEquals(tlsOptions, opts.getRpcOptions().getTlsOptions());
 
         RouterOptions routerOptions = opts.getRouterOptions();
         Assert.assertNotNull(routerOptions);

ingester-rpc/src/main/java/io/greptime/rpc/RpcOptions.java

@@ -16,7 +16,6 @@
 package io.greptime.rpc;
 
 import io.greptime.common.Copiable;
-import java.util.Optional;
 import java.util.concurrent.TimeUnit;
 
 /**