### Motivation

On main, the HTTPBody length type changed from Int to Int64.

### Modifications

Adapted the transport with this change.

### Result

Repo builds again when using the latest runtime.

### Test Plan

Adapted tests.

### Motivation

Part of addressing
apple/swift-openapi-generator#75 and
apple/swift-openapi-generator#119.

### Modifications

Bumped Swift tools version to 5.9 and made the `ExistentialAny` build
setting unconditional.

### Result

Building the package requires 5.9 now.

### Test Plan

Ran tests, all passed when using a Swift 5.9 toolchain.

#34)

### Motivation

We had some code in an `#if swift(<5.9)` block, which can now be removed
because we only support Swift 5.9 and newer.

### Modifications

Remove code required to support Swift 5.8.

### Result

Removed dead code.

### Test Plan

Tests pass.

### Motivation

The tests had a missing `@available` annotation which meant that they
didn't build iOS (annoyingly, when building for macOS, these things are
not checked so things were building fine locally).

### Modifications

Add missing available annotation to streaming tests.

### Result

Builds for iOS again.

### Test Plan

Local testing, selecting generic iOS destination in Xcode. This failed
before this patch, and succeeds with it.

Signed-off-by: Si Beaumont <[email protected]>

Bump to 1.0.0-alpha.1

### Motivation

Prepare for 1.0.0-alpha.1.

### Modifications

- Updated runtime dependency.
- Updated docs.

### Result

Ready to tag 1.0.0-alpha.1.

### Test Plan

All tests pass.


Reviewed by: simonjbeaumont

Builds:
     ✔︎ pull request validation (5.10) - Build finished. 
     ✔︎ pull request validation (5.9) - Build finished. 
     ✔︎ pull request validation (nightly) - Build finished. 
     ✔︎ pull request validation (soundness) - Build finished. 

#36