Improve DavException construction

[rfc2822]

After doing some research and thinking about

• what exception classes we have and what they're used for,
• how other HTTP / HTTP-using frameworks define their exceptions,
• the questions mentioned earlier

I came to this proposal that shall close #80:

a HttpResponse body may or may not be consumable (think about a streaming transfer that is already finished)

Same for the request body. DavException handles those cases and doesn't set a request/response excerpt then. Also added the JSR 305 @WillNotClose to make clear that the DavException won't close the response (so it's the responsibility of the caller, who should always use use or try/finally).

it's not clear why the whole response is needed in the exception,

It's handy for constructing the response. This pattern is also used for instance in Ktor's ResponseException.

it could cause problems when we try to serialize the exception,

True → added test for JVM serialization, because Exception base class is Serializable.

it couples a HTTP-level data class with a specific HTTP implementation.

Only for construction. To make this clear, I changed the primary constructor so that it takes only simple values. HttpResponse parsing is moved to a secondary constructor.

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Further notes / changes:

• Simplified request / response body logic and XML error extraction.
• Exceptions for specific HTTP error codes now validate the error code to avoid mistakes.
• Make InvalidPropertyException a subclass of DavException.
• Simplify DavResource.checkStatus().
• Made Error a data class so that it prints the error names in toString() and errors can be compared.

[Copilot]

Pull Request Overview

This PR improves DavException construction by refactoring how HTTP responses are handled in exceptions and simplifying the exception hierarchy. The changes focus on making exception construction more type-safe and removing serialization concerns.

• Restructured DavException to have a primary constructor with simple parameters and a secondary constructor for HTTP response parsing
• Added validation to specific HTTP exception subclasses to ensure they're only created with the correct status codes
• Simplified exception construction logic and removed serialization support

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
src/main/kotlin/at/bitfire/dav4jvm/exception/DavException.kt	Major refactoring of primary constructor and HTTP response parsing logic
src/main/kotlin/at/bitfire/dav4jvm/exception/HttpException.kt	Simplified to only accept Response objects, removed status code constructor
src/main/kotlin/at/bitfire/dav4jvm/exception/*Exception.kt	Added status code validation to specific HTTP exception subclasses
src/main/kotlin/at/bitfire/dav4jvm/DavResource.kt	Updated exception construction and simplified checkStatus method
src/main/kotlin/at/bitfire/dav4jvm/Error.kt	Made Error a data class for better toString and comparison
src/test/kotlin/at/bitfire/dav4jvm/exception/*Test.kt	Updated tests to reflect new property names and construction patterns
gradle/libs.versions.toml	Added SpotBugs annotations dependency

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[Copilot]

Pull Request Overview

This PR refactors the DavException construction to improve its design and usability. The main purpose is to decouple HTTP response parsing from the primary constructor while maintaining backwards compatibility and improving error handling.

Key Changes

• Changed DavException primary constructor to accept simple values instead of HTTP response objects
• Added validation to HTTP exception subclasses to ensure correct status codes
• Made Error class a data class for better debugging and comparison capabilities

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/main/kotlin/at/bitfire/dav4jvm/exception/DavException.kt	Complete refactor of exception construction with new primary constructor and response parsing logic
src/main/kotlin/at/bitfire/dav4jvm/exception/HttpException.kt	Simplified to only accept Response objects, removing dual constructor pattern
src/main/kotlin/at/bitfire/dav4jvm/exception/*.kt	Added status code validation to specific HTTP exception classes
src/main/kotlin/at/bitfire/dav4jvm/Error.kt	Converted to data class for better toString() and equality support
src/test/kotlin/at/bitfire/dav4jvm/exception/DavExceptionTest.kt	Comprehensive rewrite of tests to cover new functionality
src/main/kotlin/at/bitfire/dav4jvm/DavResource.kt	Updated to use new exception constructors and simplified checkStatus method

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