fix Server model; add redis components for guestbook app

[amyXia1994]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• [ ] N
• [X] Y

the modification on the server model/backend/render is to fix #81 the modification on the guestbook demo is related to https://github.com/KusionStack/kusionstack.io/issues/175

2. What is the scope of this PR (e.g. component or file name):

• server model frontend/backend/render
• guestbook demo

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• fix Server model: allow multiple components app defined in one stack
• update guestbook demo: add backend redis to make it a complete app

• [ ] Affects user behaviors
• [ ] Contains syntax changes
• [ ] Contains variable changes
• [ ] Contains experimental features
• [ ] Performance regression: Consumes more CPU
• [ ] Performance regression: Consumes more Memory
• [ ] Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• [X] N
• [ ] Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• [ ] Unit test
• [ ] Integration test
• [ ] Benchmark (add benchmark stats below)
• [ ] Manual test (add detailed scripts or steps below)
• [X] Other

the appops/guestbook project can be a demo to verify the modification on the server model

6. Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

bugFix: fix the Server model to allow multiple components defined in a single stack.

[howieyuen]

I think labels have its own meanings, following snippet would be better:

app.kubernetes.io/project: guestbook
app.kubernetes.io/stack: dev
app.kubernetes.io/instance: guestbook-dev
app.kubernetes.io/app: redis-leader

[amyXia1994]

I think labels have its own meanings, following snippet would be better:

app.kubernetes.io/project: guestbook
app.kubernetes.io/stack: dev
app.kubernetes.io/instance: guestbook-dev
app.kubernetes.io/app: redis-leader

I agree with you, but that will change the implication of the app.kubernetes.io/app label and will impact the already existing resources. If we change the labels like that, then app.kubernetes.io/project means the old "META APP" concept and app.kubernetes.io/app identifies a server

cc @SparkYuan

[SparkYuan]

@amyXia1994 In most scenarios, there is only one workload in one project/app. Maybe you can change this label to app.kubernetes.io/component to make this label easier to understand

[amyXia1994]

@amyXia1994 In most scenarios, there is only one workload in one project/app. Maybe you can change this label to app.kubernetes.io/component to make this label easier to understand

updated, ptal