Add EndpointParam entity for database table mapping

Introduced the `EndpointParam` class to represent the `TBREC_CFG_ENDPOINT_PARAMS` table in the database.

- Added `using` directives for data annotations and table mapping.
- Defined properties to map to table columns, all nullable for flexibility.
- Annotated the class with `[Table]` and properties with `[Column]` attributes.
- Marked `Guid` as the primary key using the `[Key]` attribute.
- Documented the class with a summary explaining its purpose and design.

This change facilitates ORM integration and ensures schema flexibility.

src/ReC.Domain/Entities/EndpointParam.cs

@@ -0,0 +1,47 @@
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace ReC.Domain.Entities;
+
+/// <summary>
+/// Represents the TBREC_CFG_ENDPOINT_PARAMS table.
+/// All properties are nullable to provide flexibility on the database side,
+/// preventing breaking changes if columns are altered to be nullable in production.
+/// </summary>
+[Table("TBREC_CFG_ENDPOINT_PARAMS", Schema = "dbo")]
+public class EndpointParam
+{
+    [Key]
+    [Column("GUID")]
+    public long? Guid { get; set; }
+
+    [Column("ACTIVE")]
+    public bool? Active { get; set; }
+
+    [Column("DESCRIPTION")]
+    public string? Description { get; set; }
+
+    [Column("GROUP_ID")]
+    public short? GroupId { get; set; }
+
+    [Column("SEQUENCE")]
+    public byte? Sequence { get; set; }
+
+    [Column("KEY")]
+    public string? Key { get; set; }
+
+    [Column("VALUE")]
+    public string? Value { get; set; }
+
+    [Column("ADDED_WHO")]
+    public string? AddedWho { get; set; }
+
+    [Column("ADDED_WHEN")]
+    public DateTime? AddedWhen { get; set; }
+
+    [Column("CHANGED_WHO")]
+    public string? ChangedWho { get; set; }
+
+    [Column("CHANGED_WHEN")]
+    public DateTime? ChangedWhen { get; set; }
+}