Add integration for Flyway

[TheBlueSky]

Closes #1066

This PR adds the base Flyway integration and the first of several Flyway database resource integration, PostgreSQL.

PR Checklist

• Created a feature/dev branch in your fork (vs. submitting directly from a commit on main)
• Based off latest main branch of toolkit
• PR doesn't include merge commits (always rebase on top of our main, if needed)
• New integration
  • Docs are written
  • Added description of major feature to project description for NuGet package (4000 total character limit, so don't push entire description over that)
• Tests for the changes have been added (for bug fixes / features) (if applicable)
• Contains NO breaking changes
• Every new API (including internal ones) has full XML docs
• Code follows all style conventions

Other information

None.

[Copilot]

Pull request overview

This PR adds a new Flyway integration for .NET Aspire, enabling database migration capabilities. Flyway is a popular database migration tool that supports multiple database systems. The integration includes the base Flyway hosting package and PostgreSQL-specific extensions as the first database implementation.

• Adds CommunityToolkit.Aspire.Hosting.Flyway package with core Flyway resource definitions and configuration
• Adds PostgreSQL extension methods (WithFlywayMigration and WithFlywayRepair) to the PostgreSQL.Extensions package
• Includes comprehensive tests and four example projects demonstrating various usage scenarios

Reviewed changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated 24 comments.

Show a summary per file

File	Description
src/CommunityToolkit.Aspire.Hosting.Flyway/FlywayResource.cs	Defines the core FlywayResource as a ContainerResource
src/CommunityToolkit.Aspire.Hosting.Flyway/FlywayResourceConfiguration.cs	Configuration model for Flyway container image and migration scripts path
src/CommunityToolkit.Aspire.Hosting.Flyway/DistributedApplicationBuilderExtensions.cs	Extension methods to add Flyway resources to the application builder
src/CommunityToolkit.Aspire.Hosting.Flyway/FlywayResourceBuilderExtensions.cs	Extension method for telemetry opt-in configuration
src/CommunityToolkit.Aspire.Hosting.Flyway/README.md	Documentation for the base Flyway integration
src/CommunityToolkit.Aspire.Hosting.Flyway/CommunityToolkit.Aspire.Hosting.Flyway.csproj	Project file for the Flyway integration package
src/CommunityToolkit.Aspire.Hosting.PostgreSQL.Extensions/PostgresDatabaseResourceBuilderExtensions.cs	PostgreSQL-specific extension methods for Flyway migration and repair
src/CommunityToolkit.Aspire.Hosting.PostgreSQL.Extensions/README.md	Updated documentation including Flyway usage examples
src/CommunityToolkit.Aspire.Hosting.PostgreSQL.Extensions/CommunityToolkit.Aspire.Hosting.PostgreSQL.Extensions.csproj	Added project reference to Flyway package
tests/CommunityToolkit.Aspire.Hosting.Flyway.Tests/*	Unit tests for core Flyway functionality
tests/CommunityToolkit.Aspire.Hosting.PostgreSQL.Extensions.Tests/ResourceCreationTests.cs	Tests for PostgreSQL Flyway integration
examples/flyway/*	Four example projects demonstrating basic usage, container configuration, custom configuration, and repair scenarios
CommunityToolkit.Aspire.slnx	Updated solution file to include new projects

[aaronpowell]

Overall it's pretty bang on, just a small change around how the container image is defined and used to ensure consistency, and you'll need to run generate-test-list-for-workflow.sh to update the tests workflow to ensure the tests are run.