feat(domain): add POP3 and OAuth2 credential fields to EmailAccount entity

src/core/DigitalData.MessagingService.Domain/Entities/EmailAccount.cs

@@ -72,4 +72,45 @@ public class EmailAccount
     /// </summary>
     [Column("IMAP_USE_SSL", TypeName = "bit")]
     public bool ImapUseSsl { get; set; } = true;
+
+    /// <summary>
+    /// POP3 server hostname (e.g. "pop.example.com").
+    /// Leave empty when this account does not use POP3.
+    /// </summary>
+    [MaxLength(256)]
+    [Column("POP3_SERVER", TypeName = "nvarchar(256)")]
+    public string? Pop3Server { get; set; }
+
+    /// <summary>
+    /// POP3 server port (995 for SSL, 110 for plain).
+    /// </summary>
+    [Column("POP3_PORT", TypeName = "int")]
+    public int Pop3Port { get; set; } = 995;
+
+    /// <summary>
+    /// Use SSL/TLS when connecting to the POP3 server.
+    /// </summary>
+    [Column("POP3_USE_SSL", TypeName = "bit")]
+    public bool Pop3UseSsl { get; set; } = true;
+
+    /// <summary>
+    /// OAuth2 client ID (required when <see cref="UseOAuth2"/> is true).
+    /// </summary>
+    [MaxLength(512)]
+    [Column("OAUTH2_CLIENT_ID", TypeName = "nvarchar(512)")]
+    public string? OAuth2ClientId { get; set; }
+
+    /// <summary>
+    /// OAuth2 client secret (required when <see cref="UseOAuth2"/> is true).
+    /// </summary>
+    [MaxLength(512)]
+    [Column("OAUTH2_CLIENT_SECRET", TypeName = "nvarchar(512)")]
+    public string? OAuth2ClientSecret { get; set; }
+
+    /// <summary>
+    /// OAuth2 tenant ID (e.g. for Microsoft 365: tenant GUID or "common").
+    /// </summary>
+    [MaxLength(256)]
+    [Column("OAUTH2_TENANT_ID", TypeName = "nvarchar(256)")]
+    public string? OAuth2TenantId { get; set; }
 }