Add server validation of interaction inputs

[JamesNK]

Description

Validate interaction service input matches what is expected:

• Required inputs have a value
• Number inputs are a number
• Boolean inputs are a boolean
• Choice inputs are one of the options
• Give text inputs a configurable max length. Default value of 8000 should be large enough for any normal usage. Could add configuration for a custom length in the future

The dashboard or CLI shouldn't send these values, UI logic should prevent that from happening, but server should double check.

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire-docs issue (consider using one of the following templates):
      • New (or update) doc-idea template
      • New breaking-change template
      • New diagnostic template
  • No

[Copilot]

Pull Request Overview

This PR adds comprehensive server-side validation for interaction service inputs to ensure data integrity and provide clear error messages to users. The validation covers all input types with appropriate type checking and constraint enforcement.

• Validates required inputs, data types (number, boolean), choice options, and text length limits
• Adds server-side validation that runs before custom validation callbacks
• Implements a maximum text length of 8000 characters for text inputs with corresponding UI enforcement

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Aspire.Hosting/InteractionService.cs	Core validation logic for all input types with error handling
src/Aspire.Hosting/IInteractionService.cs	Defines maximum text length constant for validation
src/Aspire.Dashboard/Components/Dialogs/InteractionsInputDialog.razor.cs	Dashboard constant for text length matching server validation
src/Aspire.Dashboard/Components/Dialogs/InteractionsInputDialog.razor	UI enforcement of maximum text length on input fields
tests/Aspire.Hosting.Tests/InteractionServiceTests.cs	Comprehensive test coverage for all validation scenarios

[Copilot]

The MaxTextLength constant is duplicated between InteractionInput and InteractionsInputDialog. Consider referencing the constant from InteractionInput instead of duplicating it to maintain a single source of truth.

[davidfowl]

If this makes back porting harder then we shouldn’t merge this or we should backport it

[JamesNK]

This is security hardening and should be in 9.4

[davidfowl]

Could add configuration for a custom length in the future

Lets add this.

[JamesNK]

Could add configuration for a custom length in the future

Lets add this.

Done

[JamesNK]

/backport to release/9.4

[github-actions]

Started backporting to release/9.4: https://github.com/dotnet/aspire/actions/runs/16387420476