chore: add hrynco common library solution

- add the standalone HrynCo.Common solution and projects
- include the shared common library source and tests
- add package metadata and a repo gitignore

HrynCo.Common/HealthChecks/BaseConfigurationCheck.cs

@@ -0,0 +1,39 @@
+namespace HrynCo.Common.HealthChecks;
+
+using System.ComponentModel.DataAnnotations;
+using HrynCo.Common.HealthChecks.Interfaces;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public abstract class BaseConfigurationCheck<TOptions> : IConfigurationCheck
+    where TOptions : class
+{
+    private readonly string _name;
+    private readonly TOptions _options;
+
+    protected BaseConfigurationCheck(TOptions options, string name)
+    {
+        _options = options;
+        _name = name;
+    }
+
+    public Task<HealthCheckResult> CheckConfigurationAsync(CancellationToken cancellationToken)
+    {
+        var context = new ValidationContext(_options);
+        var results = new List<ValidationResult>();
+
+        bool isValid = Validator.TryValidateObject(
+            _options,
+            context,
+            results,
+            true
+        );
+
+        if (!isValid)
+        {
+            string errors = string.Join("; ", results.Select(r => r.ErrorMessage));
+            return Task.FromResult(HealthCheckResult.Unhealthy($"{_name} configuration invalid: {errors}"));
+        }
+
+        return Task.FromResult(HealthCheckResult.Healthy($"{_name} configuration is valid."));
+    }
+}

HrynCo.Common/HealthChecks/CompositeHealthCheck.cs

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+namespace HrynCo.Common.HealthChecks;
+
+using HrynCo.Common.HealthChecks.Interfaces;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public class CompositeHealthCheck : IHealthCheck
+{
+    private readonly IConfigurationCheck _configCheck;
+    private readonly bool _configOnly;
+    private readonly IServiceHealthCheck _serviceCheck;
+
+    public CompositeHealthCheck(
+        IConfigurationCheck configCheck,
+        IServiceHealthCheck serviceCheck,
+        bool configOnly)
+    {
+        _configCheck = configCheck;
+        _serviceCheck = serviceCheck;
+        _configOnly = configOnly;
+    }
+
+    public Task<HealthCheckResult> CheckHealthAsync(
+        HealthCheckContext context,
+        CancellationToken cancellationToken)
+    {
+        return _configOnly
+            ? _configCheck.CheckConfigurationAsync(cancellationToken)
+            : _serviceCheck.CheckHealthAsync(cancellationToken);
+    }
+}

HrynCo.Common/HealthChecks/Defaults/DbOptions.cs

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+namespace HrynCo.Common.HealthChecks.Defaults;
+
+using System.ComponentModel.DataAnnotations;
+
+public class DbOptions
+{
+    [Required]
+    public string? ConnectionString { get; set; } = null!;
+}

HrynCo.Common/HealthChecks/Defaults/DbServiceHealthCheck.cs

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+namespace HrynCo.Common.HealthChecks.Defaults;
+
+using HrynCo.Common.HealthChecks.Interfaces;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public sealed class DbServiceHealthCheck : IServiceHealthCheck
+{
+    private readonly IDatabaseConnectionChecker _checker;
+
+    public DbServiceHealthCheck(IDatabaseConnectionChecker checker)
+    {
+        _checker = checker;
+    }
+
+    public async Task<HealthCheckResult> CheckHealthAsync(CancellationToken cancellationToken)
+    {
+        return await _checker.CanConnectAsync(cancellationToken)
+            ? HealthCheckResult.Healthy("Database reachable")
+            : HealthCheckResult.Unhealthy("Database unreachable");
+    }
+}

HrynCo.Common/HealthChecks/Defaults/SeqOptions.cs

@@ -0,0 +1,9 @@
+namespace HrynCo.Common.HealthChecks.Defaults;
+
+using System.ComponentModel.DataAnnotations;
+
+public class SeqOptions
+{
+    [Required]
+    public string? ServerUrl { get; set; }
+}

HrynCo.Common/HealthChecks/Interfaces/IConfigurationCheck.cs

@@ -0,0 +1,8 @@
+namespace HrynCo.Common.HealthChecks.Interfaces;
+
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public interface IConfigurationCheck
+{
+    Task<HealthCheckResult> CheckConfigurationAsync(CancellationToken cancellationToken);
+}

HrynCo.Common/HealthChecks/Interfaces/IDatabaseConnectionChecker.cs

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+namespace HrynCo.Common.HealthChecks.Interfaces;
+
+public interface IDatabaseConnectionChecker
+{
+    Task<bool> CanConnectAsync(CancellationToken cancellationToken);
+}

HrynCo.Common/HealthChecks/Interfaces/IServiceHealthCheck.cs

@@ -0,0 +1,8 @@
+namespace HrynCo.Common.HealthChecks.Interfaces;
+
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+public interface IServiceHealthCheck
+{
+    Task<HealthCheckResult> CheckHealthAsync(CancellationToken cancellationToken);
+}