feat(db): add postgres setup and multi-tenant config

src/main/java/com/caspos/config/tenant/SchemaBasedMultiTenantConnectionProvider.java

@@ -0,0 +1,62 @@
+package com.caspos.config.tenant;
+
+import org.hibernate.engine.jdbc.connections.spi.MultiTenantConnectionProvider;
+import org.springframework.stereotype.Component;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+
+@Component
+public class SchemaBasedMultiTenantConnectionProvider implements MultiTenantConnectionProvider<String> {
+
+    private final DataSource dataSource;
+
+    public SchemaBasedMultiTenantConnectionProvider(DataSource dataSource) {
+        this.dataSource = dataSource;
+    }
+
+    @Override
+    public Connection getAnyConnection() throws SQLException {
+        return dataSource.getConnection();
+    }
+
+    @Override
+    public void releaseAnyConnection(Connection connection) throws SQLException {
+        connection.close();
+    }
+
+    @Override
+    public Connection getConnection(String tenantIdentifier) throws SQLException {
+        final Connection connection = getAnyConnection();
+        connection.setSchema(tenantIdentifier);
+        return connection;
+    }
+
+    @Override
+    public void releaseConnection(String tenantIdentifier, Connection connection) throws SQLException {
+        try {
+            connection.setSchema("public");
+        } finally {
+            releaseAnyConnection(connection);
+        }
+    }
+
+    @Override
+    public boolean supportsAggressiveRelease() {
+        return true;
+    }
+
+    @Override
+    public boolean isUnwrappableAs(Class<?> unwrapType) {
+        return MultiTenantConnectionProvider.class.isAssignableFrom(unwrapType);
+    }
+
+    @Override
+    public <T> T unwrap(Class<T> unwrapType) {
+        if (isUnwrappableAs(unwrapType)) {
+            return unwrapType.cast(this);
+        }
+        throw new IllegalArgumentException("Can't unwrap to " + unwrapType.getName());
+    }
+}

src/main/java/com/caspos/config/tenant/TenantContext.java

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+package com.caspos.config.tenant;
+
+public final class TenantContext {
+
+    private static final String DEFAULT_TENANT = "public";
+    private static final ThreadLocal<String> CURRENT_TENANT = ThreadLocal.withInitial(() -> DEFAULT_TENANT);
+
+    private TenantContext() {}
+
+    public static String getCurrentTenant() {
+        return CURRENT_TENANT.get();
+    }
+
+    public static void setCurrentTenant(String tenantSchema) {
+        if (tenantSchema == null || tenantSchema.isBlank()) {
+            CURRENT_TENANT.set(DEFAULT_TENANT);
+        } else {
+            CURRENT_TENANT.set(tenantSchema);
+        }
+    }
+
+    public static void clear() {
+        CURRENT_TENANT.set(DEFAULT_TENANT);
+    }
+}

src/main/java/com/caspos/config/tenant/TenantIdentifierResolver.java

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+package com.caspos.config.tenant;
+
+import org.hibernate.context.spi.CurrentTenantIdentifierResolver;
+import org.springframework.stereotype.Component;
+
+@Component
+public class TenantIdentifierResolver implements CurrentTenantIdentifierResolver<String> {
+
+    @Override
+    public String resolveCurrentTenantIdentifier() {
+        String tenant = TenantContext.getCurrentTenant();
+        return (tenant != null && !tenant.isBlank()) ? tenant : "public";
+    }
+
+    @Override
+    public boolean validateExistingCurrentSessions() {
+        return true;
+    }
+}