Align and consolidate cache expiration settings across CacheService

[Copilot]

Cache durations across services were inconsistent—some cached for 12 hours, others for 1 hour, with no centralized policy. This consolidates all cache TTLs into four standardized tiers.

Centralized CacheDurations constants

New static class in core/Microsoft.Mcp.Core/src/Services/Caching/CacheDurations.cs:

Tier	Duration	Rationale
Tenant	12h	Rarely changes
Subscription	2h	Relatively stable
AuthenticatedClient	15min	SDK client instances
ServiceData	5min	User-facing resource data

// Before: each service defined its own ad-hoc duration
private static readonly TimeSpan s_cacheDuration = TimeSpan.FromHours(1);

// After: references centralized constant
private static readonly TimeSpan s_cacheDuration = CacheDurations.ServiceData;

Duration changes

• SubscriptionService: 12h → 2h
• ResourceGroupService, AksService, FunctionAppService, SignalRService: 1h → 5min
• KustoService: data 1h → 5min, clients 2h → 15min
• SearchService: services 1h → 5min (clients already 15min)
• CosmosService: split single 15min duration into AuthenticatedClient (15min) for CosmosClient instances and ServiceData (5min) for database/container lists
• TenantService: no value change, now references CacheDurations.Tenant

Tests

Added CacheDurationsTests validating all four tier values and their ordering.

Invoking Livetests

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Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• learn.microsoft.com
  • Triggering command: /home/REDACTED/work/mcp/mcp/core/Azure.Mcp.Core/tests/Azure.Mcp.Core.UnitTests/bin/Debug/net10.0/Azure.Mcp.Core.UnitTests /home/REDACTED/work/mcp/mcp/core/Azure.Mcp.Core/tests/Azure.Mcp.Core.UnitTests/bin/Debug/net10.0/Azure.Mcp.Core.UnitTests @@ /tmp/tmpgty3Y9.tmp grep -l ICacheService ice.cs /usr/bin/grep (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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