feat(authorization): add permission policy

src/BuildingBlocks/Contracts/Authorization/AuthorizationPolicy.cs

@@ -0,0 +1,35 @@
+namespace OpenHealthOS.Contracts.Authorization;
+
+/// <summary>
+/// Represents a named authorization policy.
+/// </summary>
+public sealed record AuthorizationPolicy
+{
+    /// <summary>
+    /// Initializes a new instance of the
+    /// <see cref="AuthorizationPolicy"/> class.
+    /// </summary>
+    /// <param name="value">The stable policy identifier.</param>
+    public AuthorizationPolicy(string value)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            throw new ArgumentException(
+                "Authorization policy value cannot be null or whitespace.",
+                nameof(value));
+        }
+
+        Value = value;
+    }
+
+    /// <summary>
+    /// Gets the stable policy identifier.
+    /// </summary>
+    public string Value { get; }
+
+    /// <summary>
+    /// Returns the policy identifier.
+    /// </summary>
+    /// <returns>The policy identifier string.</returns>
+    public override string ToString() => Value;
+}

src/BuildingBlocks/Security/Authorization/IAuthorizationPolicy.cs

@@ -0,0 +1,23 @@
+namespace OpenHealthOS.Security.Authorization;
+
+using OpenHealthOS.Contracts.Authorization;
+
+/// <summary>
+/// Represents a policy used to determine whether an authorization
+/// request satisfies a defined authorization rule.
+/// </summary>
+public interface IAuthorizationPolicy
+{
+    /// <summary>
+    /// Determines whether the specified authorization context satisfies
+    /// this policy.
+    /// </summary>
+    /// <param name="context">
+    /// The authorization context to evaluate.
+    /// </param>
+    /// <returns>
+    /// <see langword="true"/> when the context satisfies the policy;
+    /// otherwise <see langword="false"/>.
+    /// </returns>
+    bool IsSatisfied(AuthorizationContextDto context);
+}

src/BuildingBlocks/Security/Authorization/PermissionPolicy.cs

@@ -0,0 +1,44 @@
+namespace OpenHealthOS.Security.Authorization;
+
+using OpenHealthOS.Contracts.Authorization;
+
+/// <summary>
+/// Authorization policy that requires a specific permission.
+/// </summary>
+public sealed class PermissionPolicy : IAuthorizationPolicy
+{
+    private readonly Permission _permission;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PermissionPolicy"/> class.
+    /// </summary>
+    /// <param name="permission">
+    /// The permission required by this policy.
+    /// </param>
+    public PermissionPolicy(Permission permission)
+    {
+        ArgumentNullException.ThrowIfNull(permission);
+
+        _permission = permission;
+    }
+
+    /// <summary>
+    /// Determines whether the authorization context satisfies the policy.
+    /// </summary>
+    /// <param name="context">
+    /// The authorization context to evaluate.
+    /// </param>
+    /// <returns>
+    /// <see langword="true"/> when the requested permission matches the
+    /// policy permission; otherwise <see langword="false"/>.
+    /// </returns>
+    public bool IsSatisfied(AuthorizationContextDto context)
+    {
+        ArgumentNullException.ThrowIfNull(context);
+
+        return string.Equals(
+            context.Permission.Value,
+            _permission.Value,
+            StringComparison.OrdinalIgnoreCase);
+    }
+}

tests/UnitTests/Authorization/PermissionPolicyTests.cs

@@ -0,0 +1,63 @@
+namespace OpenHealthOS.UnitTests.Authorization;
+
+using OpenHealthOS.Contracts.Authorization;
+using OpenHealthOS.Contracts.Identity;
+using OpenHealthOS.Security.Authorization;
+using Xunit;
+
+public sealed class PermissionPolicyTests
+{
+    [Fact]
+    public void IsSatisfied_ShouldReturnTrue_WhenPermissionMatches()
+    {
+        var policy = new PermissionPolicy(
+            new Permission("patient.read"));
+
+        var context = CreateContext("patient.read");
+
+        var result = policy.IsSatisfied(context);
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void IsSatisfied_ShouldReturnTrue_WhenPermissionMatchesIgnoringCase()
+    {
+        var policy = new PermissionPolicy(
+            new Permission("patient.read"));
+
+        var context = CreateContext("PATIENT.READ");
+
+        var result = policy.IsSatisfied(context);
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void IsSatisfied_ShouldReturnFalse_WhenPermissionDoesNotMatch()
+    {
+        var policy = new PermissionPolicy(
+            new Permission("patient.read"));
+
+        var context = CreateContext("patient.write");
+
+        var result = policy.IsSatisfied(context);
+
+        Assert.False(result);
+    }
+
+    private static AuthorizationContextDto CreateContext(
+        string permission)
+    {
+        return new AuthorizationContextDto
+        {
+            Identity = new IdentityContextDto
+            {
+                SubjectId = "test-user",
+                PrincipalType = PrincipalType.User,
+            },
+            Permission = new Permission(permission),
+            ResourceType = "Patient",
+        };
+    }
+}