Refactor solution structure and add RabbitMQ config

Reorganized the solution structure to align with a layered architecture:
- Replaced `src` folder with `core`, `infrastructure`, and `presentation`.
- Moved projects to their respective folders.
- Added `DigitalData.MessagingService.Publisher.Abstraction` project.
- Removed `DigitalData.MessagingService.Client` project.

Updated project configurations and nesting in the solution file.

Added `appsettings.Secrets.json` with RabbitMQ and email account settings:
- RabbitMQ configuration includes hostname, port, credentials, and queue/exchange details.
- Email configuration includes SMTP server details and credentials.

src/infrastructure/DigitalData.MessagingService.Infrastructure/Repositories/Repository.cs

@@ -0,0 +1,158 @@
+using System.Linq.Expressions;
+using AutoMapper;
+using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Domain.Exceptions;
+using DigitalData.MessagingService.Infrastructure.Persistence;
+using Microsoft.EntityFrameworkCore;
+
+namespace DigitalData.MessagingService.Infrastructure.Repositories;
+
+/// <summary>
+/// Generic repository implementation with AutoMapper-based CRUD operations.
+/// IMPORTANT: Each operation auto-saves changes - NO explicit SaveChangesAsync needed!
+/// </summary>
+public class Repository<TEntity>(MessagingServiceDbContext Context, IMapper Mapper) : IRepository<TEntity> where TEntity : class
+{
+    private readonly DbSet<TEntity> _dbSet = Context.Set<TEntity>();
+
+    // --- CREATE ---
+
+    public async Task<TEntity> CreateAsync<TDto>(TDto dto, CancellationToken cancellationToken = default)
+    {
+        var entity = Mapper.Map<TEntity>(dto);
+        await _dbSet.AddAsync(entity, cancellationToken);
+        await Context.SaveChangesAsync(cancellationToken);
+        return entity;
+    }
+
+    // --- READ ---
+
+    public async Task<TEntity?> GetByIdAsync(int id, CancellationToken cancellationToken = default)
+    {
+        return await _dbSet.FindAsync([id], cancellationToken);
+    }
+
+    public async Task<IEnumerable<TEntity>> GetAllAsync(CancellationToken cancellationToken = default)
+    {
+        return await _dbSet.ToListAsync(cancellationToken);
+    }
+
+    public async Task<IEnumerable<TEntity>> FindAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        int? skip = null,
+        int? take = null,
+        CancellationToken cancellationToken = default)
+    {
+        var query = _dbSet.Where(predicate);
+        
+        if (skip.HasValue)
+            query = query.Skip(skip.Value);
+        
+        if (take.HasValue)
+            query = query.Take(take.Value);
+        
+        return await query.ToListAsync(cancellationToken);
+    }
+
+    public async Task<TEntity?> FindFirstAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        CancellationToken cancellationToken = default)
+    {
+        return await _dbSet.FirstOrDefaultAsync(predicate, cancellationToken);
+    }
+
+    public async Task<TEntity?> FindSingleAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        CancellationToken cancellationToken = default)
+    {
+        return await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken);
+    }
+
+    public async Task<int> CountAsync(
+        Expression<Func<TEntity, bool>>? predicate = null,
+        CancellationToken cancellationToken = default)
+    {
+        return predicate == null
+            ? await _dbSet.CountAsync(cancellationToken)
+            : await _dbSet.CountAsync(predicate, cancellationToken);
+    }
+
+    public async Task<bool> AnyAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        CancellationToken cancellationToken = default)
+    {
+        return await _dbSet.AnyAsync(predicate, cancellationToken);
+    }
+
+    // --- UPDATE ---
+
+    /// <summary>
+    /// Updates a SINGLE entity that matches the predicate.
+    /// Throws NotFoundException if 0 or 2+ records match.
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task UpdateSingleAsync<TDto>(
+        Expression<Func<TEntity, bool>> predicate,
+        TDto dto,
+        CancellationToken cancellationToken = default)
+    {
+        var entity = await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken) 
+            ?? throw new NotFoundException($"No {typeof(TEntity).Name} found matching the predicate.");
+        Mapper.Map(dto, entity);
+        await Context.SaveChangesAsync(cancellationToken);
+    }
+
+    /// <summary>
+    /// Updates ALL entities that match the predicate (bulk operation).
+    /// Returns count of updated records.
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task<int> UpdateAsync<TDto>(
+        Expression<Func<TEntity, bool>> predicate,
+        TDto dto,
+        CancellationToken cancellationToken = default)
+    {
+        var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);
+
+        foreach (var entity in entities)
+        {
+            Mapper.Map(dto, entity);
+        }
+
+        await Context.SaveChangesAsync(cancellationToken);
+        return entities.Count;
+    }
+
+    // --- DELETE ---
+
+    /// <summary>
+    /// Deletes a SINGLE entity that matches the predicate.
+    /// Throws NotFoundException if 0 or 2+ records match.
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task DeleteSingleAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        CancellationToken cancellationToken = default)
+    {
+        var entity = await _dbSet.SingleOrDefaultAsync(predicate, cancellationToken) 
+            ?? throw new NotFoundException($"No {typeof(TEntity).Name} found matching the predicate.");
+        _dbSet.Remove(entity);
+        await Context.SaveChangesAsync(cancellationToken);
+    }
+
+    /// <summary>
+    /// Deletes ALL entities that match the predicate (bulk operation).
+    /// Returns count of deleted records.
+    /// Auto-saves changes.
+    /// </summary>
+    public async Task<int> DeleteAsync(
+        Expression<Func<TEntity, bool>> predicate,
+        CancellationToken cancellationToken = default)
+    {
+        var entities = await _dbSet.Where(predicate).ToListAsync(cancellationToken);
+
+        _dbSet.RemoveRange(entities);
+        await Context.SaveChangesAsync(cancellationToken);
+        return entities.Count;
+    }
+}