feat!: generate the REST client with OpenAPI.jl 1.x (0.5.0)

[tanmaykm]

Replaces the openapi-generator (java) client, which needed OpenAPI.jl 0.2 and JSON 0.21, with a module generated natively by OpenAPI.jl 1.1 from the same specification. Two commits: spec corrections, then the migration.

Spec corrections (commit 1)

A strict, validating client exposed places where the spec did not describe what OPA actually sends. The openapi-generator client tolerated them.

• Values OPA documents as "any JSON value" were typed object: getDocumentSuccessResponse.result (a true result failed response validation), compileSuccessResponse.result, partialQuerySchema.input/options, patchOperation.value, queryParameterPost.input, the createDocument request body. They are now untyped, matching their descriptions and the previous ::Any fields.
• inputSchema declares its single input property instead of being a free-form object.
• policy.ast.rules[].body[].terms is an object for a single term and an array for a call; it is now untyped (was object, which broke GET /v1/policies).
• GET /health 200 and DELETE /v1/policies/{id} 200 return a JSON body ({}, plus metrics for the delete) although they were declared empty; they now reference new healthyResponse / deletePolicySuccessResponse components.
• The explain enum is a named schema (explainMode) so the generated type has a stable name.

Migration (commit 2)

• specs/openapi/generate.jl regenerates src/client/OPAClient.jl in strict mode from the pinned environment in specs/openapi/Project.toml (OpenAPI 1.1.0). The generated file is committed; generate.sh and the per-model markdown tree are gone.
• The module is OPAClient; OpenPolicyAgent.Client is an alias of it, because a module cannot be named Client while defining the Client(server; kwargs...) constructor.
• Dependencies follow the emitted code: OpenAPI 1.1.1, HTTP 2, JSON 1.7, Julia ≥ 1.10 (drops 1.6–1.9); TimeZones is no longer needed (the spec has no date-time fields).
• Tests rewritten for the new API; docs (client.md, reference.md, ast_walker.md) and CI updated. docs/src/client.md has a 0.4 → 0.5 migration table.

Breaking changes for callers

0.4	0.5
OpenAPI.Clients.Client(url; escape_path_params=false)	Client.Client(url)
api = Client.DataApi(openapi_client)	no per-tag API structs; pass client as a keyword
Client.get_document_with_path(api, path, Dict("input" => x))	Client.getdocumentwithpath(path, Client.InputSchema(; input = x); client)
response, http_resp = Client.get_document(api, path)	response = Client.getdocument(path; client); with_http_info = true for an ApiResponse
Client.post_compile(api; partial_query_schema = s)	Client.postcompile(; body = s, client)
explain = true	explain = Client.ExplainMode("full")
error bodies returned as the result	Client.ApiError thrown, decoded body in ex.decoded
metrics::Dict{String,Any}	metrics structs, entries in metrics.additional_properties

Dependencies

• Requires OpenAPI.jl 1.1.1 (fix(runtime): honour allowReserved on path parameters OpenAPI.jl#112): the OPA {path} parameter is a slash-delimited document path declared allowReserved: true, and 1.1.0 percent-encodes the slashes. 1.1.1 is now registered, so this resolves.
• Set 0.4.2 #24 was released first as 0.4.2, for consumers that need JSON 1.x while still on OpenAPI.jl 0.2.

Testing

203/203 locally on Julia 1.10.11 and 1.12.7 (originally against the JuliaComputing/OpenAPI.jl#112 branch, since released as 1.1.1). CI is green on all jobs.

x86 (32-bit) has been dropped from the matrix: Reseau.jl, pulled in via HTTP 2.x, fails to precompile on i686 Linux and Windows (JuliaServices/Reseau.jl#156). 32-bit is therefore untested.