feat: add tool to generate code from spec

[tanmaykm]

Add a few methods that help invoke the code generator providing a spec file and generating Julia code.

The OpenAPI Generator Docker image is a code generator that can generate client libraries, server stubs, and API documentation from an OpenAPI Specification. It can also be hosted as a service. OpenAPI.jl will now make use of that to provide a way to generate code. Methos OpenAPI.generate will generate code from an OpenAPI specification. It can be pointed at a server hosted on the local machine or a remote server. The OpenAPI Generator must be running at the specified generator_host. Returns the folder containing generated code.

OpenAPI.generate(
    spec::Dict{String,Any};
    type::Symbol=:client,
    package_name::AbstractString="APIClient",
    export_models::Bool=false,
    export_operations::Bool=false,
    output_dir::AbstractString="",
    generator_host::AbstractString=GeneratorHost.Local
)

Arguments:

• spec: The OpenAPI specification as a Dict. It can be obtained by parsing a JSON or YAML file using JSON.parse or YAML.load.

Optional arguments:

• type: The type of code to generate. Must be :client or :server. Defaults to :client.
• package_name: The name of the package to generate. Defaults to "APIClient".
• export_models: Whether to export models. Defaults to false.
• export_operations: Whether to export operations. Defaults to false.
• output_dir: The directory to save the generated code. Defaults to a temporary directory. Directory will be created if it does not exist.
• generator_host: The host of the OpenAPI Generator. Defaults to GeneratorHost.Local (which points to http://localhost:8080).

The generator_host can be pointed to any other URL where the OpenAPI Generator is running, e.g. https://openapigen.myorg.com. Other possible pre-defined values of generator_host, which point to the public service hosted by OpenAPI org are:

• OpenAPI.GeneratorHost.OpenAPIGeneratorTech.Stable: Runs a stable version of the OpenAPI Generator at https://api.openapi-generator.tech.
• OpenAPI.GeneratorHost.OpenAPIGeneratorTech.Master: Runs the latest version of the OpenAPI Generator at https://api-latest-master.openapi-generator.tech.

A locally hosted generator service is preferred by default for privacy reasons. One can be started on the local machine using OpenAPI.openapi_generator. It uses the openapitools/openapi-generator-online docker image and requires docker engine to be installed. Use OpenAPI.stop_openapi_generator to stop the local generator service after use.

OpenAPI.openapi_generator(;
    port::Int=8080,         # port to use
    use_sudo::Bool=false    # whether to use sudo while invoking docker
)

OpenAPI.stop_openapi_generator(;
    use_sudo::Bool=false    # whether to use sudo while invoking docker
)