Closes #17689

This PR optimizes the audit logs query performance by extracting the
count operation into a separate query and replacing the OR-based
workspace_builds with conditional joins.

## Query changes
* Extracted count query to separate one
* Replaced single `workspace_builds` join with OR conditions with
separate conditional joins
* Added conditional joins
* `wb_build` for workspace_build audit logs (which is a direct lookup)
    * `wb_workspace` for workspace create audit logs (via workspace)

Optimized AuditLogsOffset query:
https://explain.dalibo.com/plan/4g1hbedg4a564bg8

New CountAuditLogs query:
https://explain.dalibo.com/plan/ga2fbcecb9efbce3

Fixes coder/internal#715

After this change, the only use of the `workspace_prebuilds` view is the
`ClaimPrebuiltWorkspace` query. A subsequent PR will update the view.

Before: ~44ms https://explain.dalibo.com/plan/76cbe21d1a4c9329#plan

After: 7.3ms https://explain.dalibo.com/plan/5abbdf926315677e#plan

Reset the error associated with a devcontainer when a rebuild is requested.

Previously, by mistake, the task sidebar would not display workspace
apps that don't have a health check configured.

… (#18588)"

This reverts commit 258a839.

…es (#18689)

## Description

This PR adds a warning to the prebuilds documentation about
incompatibility with Workspace schedule (autostart/autostop), dormancy,
and DevContainers. These configurations can interfere with prebuild
behavior and should be avoided for now.

Preview:
![Screenshot 2025-07-01 at 12 58
02](https://github.com/user-attachments/assets/e1a837de-b66c-4414-bd0b-471474b43b84)

Increase prebuilds reconciliation and backoff interval to 1 minute by
default.

…pport (#18548)

## Summary

  This PR implements critical MCP OAuth2 compliance features for Coder's authorization server, adding PKCE support, resource parameter handling, and OAuth2 server metadata discovery. This brings Coder's OAuth2 implementation significantly closer to production readiness for MCP (Model Context Protocol)
  integrations.

  ## What's Added

  ### OAuth2 Authorization Server Metadata (RFC 8414)
  - Add `/.well-known/oauth-authorization-server` endpoint for automatic client discovery
  - Returns standardized metadata including supported grant types, response types, and PKCE methods
  - Essential for MCP client compatibility and OAuth2 standards compliance

  ### PKCE Support (RFC 7636)
  - Implement Proof Key for Code Exchange with S256 challenge method
  - Add `code_challenge` and `code_challenge_method` parameters to authorization flow
  - Add `code_verifier` validation in token exchange
  - Provides enhanced security for public clients (mobile apps, CLIs)

  ### Resource Parameter Support (RFC 8707)
  - Add `resource` parameter to authorization and token endpoints
  - Store resource URI and bind tokens to specific audiences
  - Critical for MCP's resource-bound token model

  ### Enhanced OAuth2 Error Handling
  - Add OAuth2-compliant error responses with proper error codes
  - Use standard error format: `{"error": "code", "error_description": "details"}`
  - Improve error consistency across OAuth2 endpoints

  ### Authorization UI Improvements
  - Fix authorization flow to use POST-based consent instead of GET redirects
  - Remove dependency on referer headers for security decisions
  - Improve CSRF protection with proper state parameter validation

  ## Why This Matters

  **For MCP Integration:** MCP requires OAuth2 authorization servers to support PKCE, resource parameters, and metadata discovery. Without these features, MCP clients cannot securely authenticate with Coder.

  **For Security:** PKCE prevents authorization code interception attacks, especially critical for public clients. Resource binding ensures tokens are only valid for intended services.

  **For Standards Compliance:** These are widely adopted OAuth2 extensions that improve interoperability with modern OAuth2 clients.

  ## Database Changes

  - **Migration 000343:** Adds `code_challenge`, `code_challenge_method`, `resource_uri` to `oauth2_provider_app_codes`
  - **Migration 000343:** Adds `audience` field to `oauth2_provider_app_tokens` for resource binding
  - **Audit Updates:** New OAuth2 fields properly tracked in audit system
  - **Backward Compatibility:** All changes maintain compatibility with existing OAuth2 flows

  ## Test Coverage

  - Comprehensive PKCE test suite in `coderd/identityprovider/pkce_test.go`
  - OAuth2 metadata endpoint tests in `coderd/oauth2_metadata_test.go`
  - Integration tests covering PKCE + resource parameter combinations
  - Negative tests for invalid PKCE verifiers and malformed requests

  ## Testing Instructions

  ```bash
  # Run the comprehensive OAuth2 test suite
  ./scripts/oauth2/test-mcp-oauth2.sh

  Manual Testing with Interactive Server

  # Start Coder in development mode
  ./scripts/develop.sh

  # In another terminal, set up test app and run interactive flow
  eval $(./scripts/oauth2/setup-test-app.sh)
  ./scripts/oauth2/test-manual-flow.sh
  # Opens browser with OAuth2 flow, handles callback automatically

  # Clean up when done
  ./scripts/oauth2/cleanup-test-app.sh

  Individual Component Testing

  # Test metadata endpoint
  curl -s http://localhost:3000/.well-known/oauth-authorization-server | jq .

  # Test PKCE generation
  ./scripts/oauth2/generate-pkce.sh

  # Run specific test suites
  go test -v ./coderd/identityprovider -run TestVerifyPKCE
  go test -v ./coderd -run TestOAuth2AuthorizationServerMetadata
```

  ### Breaking Changes

  None. All changes maintain backward compatibility with existing OAuth2 flows.

---

Change-Id: Ifbd0d9a543d545f9f56ecaa77ff2238542ff954a
Signed-off-by: Thomas Kosiewski <tk@coder.com>

The Go build cache has a tendency to accumulate and waste space
(typically in the realm of 10-70 GB). This change automatically cleans
up the cache on shutdown to prevent accumulation.