Improve string escaping and add tests (#2396)

Tighten how server URL values are emitted in the server-urls template so
that spec-supplied text is always serialized into a proper Go context:

- Route server descriptions and URLs through stripNewLines when they are
  written into generated // comments, so a multi-line value stays on the
  comment line instead of spilling into following lines.
- Emit server URL and variable-default values via toGoString (now backed
  by strconv.Quote) instead of hand-wrapping them in quotes, so quotes,
  backslashes, and newlines are escaped correctly.
- Harden StringToGoString to use strconv.Quote; the previous version only
  escaped double quotes and mishandled backslashes. This also tidies up
  the content-type literals that already used it.
- Extend stripNewLines to drop carriage returns as well as newlines.

Add regression tests covering the server-urls rendering and the
StringToGoString escaping, and confirm `make generate` produces no
changes to committed output.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

refactor(codegen): better Swagger compression, modern naming (#1909)

* refactor(codegen): better Swagger compression

* test(compatibility): Regenerate test spec

* Add GetSpec/GetSpecJSON; revert const-concat embed format

Three follow-ups to PR #1909, all in `pkg/codegen/templates/inline.tmpl`
(plus the regenerated `*.gen.go` files and migrated callers):

1. Revert the embedded spec back to `var swaggerSpec = []string{...}`.

PR #1909 replaced the historical slice-of-chunks form with a single
`const swaggerSpec = "" + "chunk" + "chunk" + ...`. With thousands of
80-char chunks (large APIs produce them) the Go compiler folds the
chained `+` at compile time, and that fold is materially slower than
parsing a slice literal. `decodeSpec` now joins the slice via
`strings.Join` before base64-decoding; flate compression, base64
encoding, the 80-char chunk size, the lazy `decodeSpecCached` /
`rawSpec` pipeline, and `PathToRawSpec` all stay exactly as PR #1909
landed them.

2. Add `GetSpec() (*openapi3.T, error)` as the canonical accessor, and
demote `GetSwagger()` to a `// Deprecated:` thin wrapper.

The kin-openapi spec type was renamed from `openapi3.Swagger` to
`openapi3.T` years ago; `GetSwagger`'s name is a stale relic. `GetSpec`
carries the body that `GetSwagger` had, and `GetSwagger` becomes a
one-line `return GetSpec()` retained for backwards compatibility.
External callers still upgrading to a newer version of oapi-codegen
will see the `// Deprecated:` hint surfaced by gopls/godoc; in-tree
callers across `examples/` and `internal/test/` are migrated to
`GetSpec()` because the repo's lint rule rejects calls into deprecated
functions and would otherwise block CI.

3. Add `GetSpecJSON() ([]byte, error)` returning the embedded JSON.

Decompressed, base64-decoded, but not unmarshaled into `*openapi3.T`.
A one-line wrapper around the existing `rawSpec()` cache, so repeated
calls don't re-decompress. This fills a long-standing gap: callers who
want to operate on the raw OpenAPI document (re-marshal to YAML, hand
to a different parser, run an overlay, dump to disk) previously had to
either invoke `openapi3.T.MarshalJSON` after `GetSpec` or hand-roll
base64+flate decode.

Migrated callers (mechanical; no logic changes):

- 7 user-side example files under `examples/` (petstore variants for
  each framework, authenticated-api echo + stdhttp).
- 12 test files under `examples/petstore-expanded/*/petstore_test.go`,
  `internal/test/externalref/imports_test.go`,
  `internal/test/issues/issue1825/overlay_test.go`,
  `internal/test/compatibility/preserve-original-operation-id-casing-in-embedded-spec/spec_test.go`.

New test:

- `examples/petstore-expanded/chi/petstore_test.go::TestSpecAccess`
  covers `GetSpec` and `GetSpecJSON` end-to-end (asserts the bytes are
  valid JSON and the parsed spec has a non-empty `OpenAPI` version
  field). `GetSwagger` is intentionally not exercised — its body is
  `return GetSpec()` and the lint rule blocks an in-tree call. If we
  later want regression coverage for the wrapper specifically, one
  test annotated with `//nolint:staticcheck // SA1019` would do it.

Verification:

- `make generate` is idempotent; spot-checking
  `examples/petstore-expanded/chi/api/petstore.gen.go` confirms the
  slice form, the three new accessors, and the `// Deprecated:` marker
  on `GetSwagger`.
- `make test` passes (exit 0) across the root module and all eight
  child modules.
- `make lint` reports `0 issues.` across the same nine modules — no
  remaining in-tree calls into the deprecated wrapper.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Marcin Romaszewicz <marcinr@gmail.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs: add example of using Renovate to sync files between repos

fix(deps): update module github.com/getkin/kin-openapi to v0.133.0 (g…

…o.mod)

docs(additional-initialisms): add a usage example

build: relax patch version pinning on `go` directive

Originally added in f77bd7b, we wanted
to pin the version to ensure that we were targeting the latest version
of Go 1.21.

However, there's no real value here, and as noted in [0] it can be
causing issues for some users.

There's nothing explicitly in Go 1.21.x that we need to pin to, just
that we need support for Go 1.21, so we can use Speakeasy's
`openapi-overlay` library.

Therefore we can relax the patch-version requirement, which will
alleviate issues for consumers.

This makes sure that we have _at a minimum_ a version of Go 1.21, and
makes `go mod tidy` happy.

[0]: osbuild/image-builder-crc#1352

docs: correct wording of heading

Update readme with install instrctions (#1652)

There are go.mod module name mismatches now that we've moved repos. Mention
this in the readme, and inform that v2.3.0 is the first working version in the
new location.

chore: deprecate v1 module

docs: add Sponsors section

Plus DevZero, our first official sponsor 👏