🐙 octavia-cli: use model serialization

[alafanechere]

What

Some shortcuts taken in the early development of the project challenge the stability of the CLI and lead to issues such as #12270

Problems and solutions

Problem: We discarded the use of model serialization
We disabled model serialization and validation on some API responses because it required updating the Open API config to declare fields as nullable (more about this here). It means the response we handled were raw python dict and not validated models.
Solution: edit airbyte-api/src/main/openapi/config.yaml to make some field nullable. Do not pass _check_return_type=False when calling endpoints to retrieve pure API client models that are validated and expose the convenient model interfaces + python casing. This allows us:

• Use snake case fields on connection and have consistent casing in generated resources (source / destination / connection). See octavia-cli/integration_tests/configurations/connections/poke_to_pg/configuration.yaml
• Build valid ConnectionUpdate and ConnectionCreate payloads with the _deserialize_raw_configuration method in octavia-cli/octavia_cli/apply/resources.py. BaseResource instances now have two configuration attributes: raw_configuration which is the content of the YAML configuration serialized as a Python dict and configuration which is the output of _deserialize_raw_configuration. By default it just extract the configuration key of raw_configuration, but for Connection this methods builds a configuration dict with value corresponding to API Client models for validation.

Problem: We used the search endpoint to retrieve remote resources
The search endpoint for connection retrieved inconsistent results when a connection was edited (which led to #12270). We used the search API endpoint in a early stage of the project when we did not persist the resource_id in the state file.
Solution: Now that we have state file we can use the get endpoints to retrieve remote resource from resource_idstored in the state. These change happen in octavia-cli/octavia_cli/apply/resources.py

Other changes

I introduced additional changes to make the code lighter and leverage inheritance as much as possible: I created a SourceAndDestination from BaseResource because Source and Destination share duplicate code otherwise.

🚨 User Impact 🚨

Connection configurations are now using snake_case instead of camel_case. Users with existing connection configuration will have to edit their configuration.yaml file for connections to change the casing.

[lmossman]

Try to catch api exception or validate existing configs to provide a understandable error message to the user directing them to switch to snake_case, or re-generate the files.

[lmossman]

Overall looks good me, if you want me to take another look after making the validation of snake_case changes, let me know

[CLAassistant]

All committers have signed the CLA.