Update the doc and comments related to setup_by_user. (#272)

Author: badmonster0

docs/docs/core/flow_def.mdx

@@ -23,7 +23,7 @@ The easiest way is to use the `@cocoindex.flow_def` decorator:
 ```python
 @cocoindex.flow_def(name="DemoFlow")
 def demo_flow(flow_builder: cocoindex.FlowBuilder, data_scope: cocoindex.DataScope):
-  ...
+    ...
 ```
 
 This `@cocoindex.flow_def` decorator declares this function as a CocoIndex flow definition.
@@ -37,7 +37,7 @@ Alternatively, for more flexibility (e.g. you want to do this conditionally or g
 
 ```python
 def demo_flow_def(flow_builder: cocoindex.FlowBuilder, data_scope: cocoindex.DataScope):
-  ...
+    ...
 
 # Add the flow definition to the flow registry.
 demo_flow = cocoindex.flow.add_flow_def("DemoFlow", demo_flow_def)
@@ -66,7 +66,7 @@ Import must happen at the top level, and the field created by import must be in
 @cocoindex.flow_def(name="DemoFlow")
 def demo_flow(flow_builder: cocoindex.FlowBuilder, data_scope: cocoindex.DataScope):
     data_scope["documents"] = flow_builder.add_source(DemoSourceSpec(...))
-  ......
+    ......
 ```
 
 </TabItem>
@@ -261,6 +261,10 @@ Export must happen at the top level of a flow, i.e. not within any child scopes
 *   `target_spec`: the storage spec as the export target.
 *   `primary_key_fields` (optional): the fields to be used as primary key. Types of the fields must be supported as key fields. See [Key Types](data_types#key-types) for more details.
 *   `vector_index` (optional): the fields to create vector index. Each item is a tuple of a field name and a similarity metric. See [Vector Type](data_types#vector-type) for more details about supported similarity metrics.
+*   `setup_by_user` (optional):
+     whether the export target is setup by user.
+     By default, CocoIndex is managing the target setup (surfaced by the `cocoindex setup` CLI subcommand), e.g. create related tables/collections/etc. with compatible schema, and update them upon change.
+     If `True`, the export target will be managed by users, and users are responsible for creating the target and updating it upon change.
 
 <Tabs>
 <TabItem value="python" label="Python" default>

src/ops/interface.rs

@@ -148,9 +148,10 @@ pub enum SetupStateCompatibility {
     /// This means the resource can be updated to the desired state without any loss of data.
     Compatible,
     /// The resource is partially compatible with the desired state.
-    /// This means some existing data will be lost after applying the setup change.
+    /// This means data from some existing fields will be lost after applying the setup change.
+    /// But at least their key fields of all rows are still preserved.
     PartialCompatible,
-    /// The resource needs to be rebuilt
+    /// The resource needs to be rebuilt. After applying the setup change, all data will be gone.
     NotCompatible,
 }