Split add and update schema apis

[lampajr]

Changes proposed

Schema

• Split add and update APIs for Schema creation and update
• Use POST for creation
• Use PUT for update
• Return 201 for creation
• Return 200 for update
• Update the tests accordingly
• Update the UI

Labels

• Split add and update APIs for Schema Labels creation and update
• Use POST for creation
• Use PUT for update
• Return 201 for creation
• Return 200 for update
• Update the tests accordingly
• Update the UI

Transformers

• Split add and update APIs for Schema Transformers creation and update
• Use POST for creation
• Use PUT for update
• Return 201 for creation
• Return 200 for update
• Update the tests accordingly
• Update the UI

Check List (Check all the applicable boxes)

• My code follows the code style of this project.
• My change requires changes to the documentation.
• I have updated the documentation accordingly.
• All new and existing tests passed.

[stalep]

I've not tested the web changes, but it looks good!