add more info to usage of generate command

base/commands/serializer/generate.go

@@ -27,7 +27,100 @@ Generates compact serializer from the given schema and for the given programming
 	long := `
 Generates compact serializer from the given schema and for the given programming language.
 You can use this command to automatically generate compact serializers instead of implementing them.
-See: https://docs.hazelcast.com/hazelcast/5.3/serialization/compact-serialization#implementing-compactserializer
+See: https://docs.hazelcast.com/hazelcast/latest/serialization/compact-serialization#implementing-compactserializer
+
+A schema allows you to:
+- describe the contents of a compact class using supported field types
+- import other schema
+- specify a namespaces for schema files and reference other namespaces
+- define cyclic references between classes
+- reference classes that are not present in the given schemas
+
+A schema is written in YAML.Schema format is given below:
+
+
+	namespace: <namespace of the class>
+	# note that other schema files can be imported with relative path to this yaml file
+	imports:
+	 - someOtherSchema.yaml
+	# All objects in this file will share the same namespace. 
+	classes:
+	 - name: <name of the class>
+	   fields:
+		 - name: <field name>
+		   type: <field type>
+		   external: bool # to mark external types (external to this yaml file)
+
+
+- namespace: 	Used for logical grouping of classes. Typically, for every namespace, you will have a schema file. 
+		Namespace is optional. If not provided, the classes will be generated at global namespace (no namespace). 
+		The user should provide the language specific best practice when using the namespace. 
+		The tool will use the namespace while generating code if provided.
+
+- imports: 	Used to import other schema files. 
+		The type definitions in the imported yaml schemas can be used within this yaml file. 
+		Cyclic imports will be checked and handled properly. 
+		For this version of the tool, an import can only be a single file name 
+		and the tool will assume all yaml files imported will be in the same directory as the importing schema file.
+
+- classes: 	Used to define classes in the schema
+ - name: 	Name of the class
+ - fields: 	Fields of the class
+  - name: 	Name of the field
+  - type: 	Type of the field. 
+		Normally you should refer to another class as namespace.classname. 
+		You can use a class without namespace when the class is defined in the same schema yaml file. 
+		type can be one of the following:
+		- boolean
+		- boolean[]
+		- int8
+		- int8[]
+		- int16
+		- int16[]
+		- int32
+		- int32[]
+		- int64
+		- int64[]
+		- float32
+		- float32[]
+		- float64
+		- float64[]
+		- string
+		- string[]
+		- date
+		- date[]
+		- time
+		- time[]
+		- timestamp
+		- timestamp[]
+		- timestampWithTimezone
+		- timestampWithTimezone[]
+		- nullableBoolean
+		- nullableBoolean[]
+		- nullableInt8
+		- nullableInt8[]
+		- nullableInt16
+		- nullableInt16[]
+		- nullableInt32
+		- nullableInt32[]
+		- nullableInt64
+		- nullableInt64[]
+		- nullableFloat32
+		- nullableFloat32[]
+		- nullableFloat64
+		- nullableFloat64[]
+		- <OtherCompactClass[]>
+  - external: 	Used to mark if the type is external. 
+		If a field is external, the tool will not check if it is imported and available. 
+		External types are managed by the user and not generated by the tool.
+		
+		The serializer of an external field can be a custom serializer which is hand written, 
+		the zero-config serializer for Java and .NET, or previously generated using the tool. 
+		This flag will enable such mixed use cases.
+		
+		In generated code, external types are imported exactly what as the "type" of the field, 
+		hence for languages like Java the user should enter the full package name together with the class. 
+		E.g. type: com.app1.dto.Address
 `
 	cc.SetCommandHelp(long, short)
 	cc.AddStringFlag(flagLanguage, "l", "", true, "programming language to use for the generated code")