docs(downgrader): OpenAPI Generator rust-axum breaks on a nullable byte string with a pattern

packages/downgrader/README.md

@@ -264,7 +264,7 @@ Accepts the default OAS dialect, which adds `discriminator`, `xml`, `externalDoc
 - An untyped schema that gains a `format` from `contentEncoding` or `contentMediaType` also gains `type: "string"`, as 3.0 binary strings need, so it rejects non-string values it accepted. 3.0 tools find file uploads only by `type: "string"` with `format: "binary"`.
 - OpenAPI Generator merges the `"null"` branch beside a `$ref` to a string enum into a new enum, so the reference is lost. In 7.17, its TypeScript Fetch client also imports each value of a query parameter that is a nullable enum, such as Zod's `z.enum(["asc", "desc"]).nullish()` in a GET input, as a model, writing `import type { 'asc', 'desc', 'null' }`, so the client does not compile. In 7.26, its Go server does not compile a property or an array item that is a nullable enum, inline or a `$ref`, such as Zod's `z.enum(["a", "b"]).nullable()`, since it checks the merged enum with an `AssertstringRequired` function it never writes. Pass `--openapi-normalizer SIMPLIFY_ONEOF_ANYOF_ENUM=false` to avoid all three.
 - OpenAPI Generator's TypeScript, Swift and Kotlin clients can leave null out of the type of an array item or map value that is a nullable `$ref` or enum, which becomes a `oneOf` with the `"null"` branch. OpenAPI Generator reads 3.1 too, which keeps it.
-- OpenAPI Generator's Rust client and its Spring server do not compile a required property that is a nullable `format: byte` string, which a nullable `contentEncoding: base64` string becomes, such as Zod's `z.base64().nullable()`. In the Rust client, an optional one can also break the optional `format: byte` properties of the models generated after it. OpenAPI Generator reads 3.1 too, which keeps the string.
+- OpenAPI Generator's Rust client and its Spring server do not compile a required property that is a nullable `format: byte` string, which a nullable `contentEncoding: base64` string becomes, such as Zod's `z.base64().nullable()`. In the Rust client, an optional one can also break the optional `format: byte` properties of the models generated after it. In 7.26, its Rust server (`rust-axum`) does not compile such a property, required or optional, when it also has a `pattern`, as Zod writes one. OpenAPI Generator reads 3.1 too, which keeps the string.
 - OpenAPI Generator's PHP client drops the namespace separators from the class of an array item that is an `allOf`, as a `$ref` with siblings becomes, writing `\OpenAPIClientModelUser[]`, so deserializing that array throws. It also writes no allowed values for the `enum` of an array item or map value that is `{ type: "null" }` alone, as Zod's `z.null()` writes there, so it rejects such an array or map unless it is empty. OpenAPI Generator reads 3.1 too, which keeps the `$ref` beside its siblings there and lets null through such an item or value.
 - OpenAPI Generator's Java client with the `native` or `jersey3` library coerces scalars while it reads a `oneOf`, and wants exactly one branch to match, so it rejects a value that two branches take once coerced, such as `1` or `"1"` against the `oneOf` that `string | number` becomes, or `true` against `string | boolean`. It also rejects null in a tuple member that may be null, as in `z.tuple([z.number(), z.string().nullable()])`, since that null sits in a branch of the `anyOf` that `items` becomes. Its Java clients and Spring server, and its C# client with the default `generichost` library, also write an enum that does not compile for `{ type: "null" }` alone, as Zod's `z.null()` writes for a property, an array item or a component, and its Python FastAPI server does for such a component. With the Java `native` or the C# `generichost` library, a union with a `contentEncoding: base64` string branch does not compile either, since they name the member for that branch, now `format: byte`, `getbyte[]` or `Byte[]`. OpenAPI Generator reads 3.1 too, which keeps the `type` list or `anyOf` and `{ type: "null" }`, leaves `prefixItems` untyped, and reads `contentEncoding` as a plain string.
 - datamodel-code-generator reads a required property with `nullable: true` as never null. Pass `--strict-nullable` to keep null. Even then, it leaves null out of an array item or map value that is a nullable array or record, such as Zod's `z.array(z.array(z.string()).nullable())`. It reads 3.1 too, which keeps the `"null"` type.