added Field class, which was missing in the previous commit

core/src/main/java/de/srsoftware/umbrella/core/Field.java

@@ -0,0 +1,51 @@
+/* © SRSoftware 2025 */
+package de.srsoftware.umbrella.core;
+
+public class Field{
+	public static final String AMOUNT = "amount";
+	public static final String BANK_ACCOUNT = "bank_account";
+	public static final String COMPANY = "company";
+	public static final String COMPANY_ID = "company_id";
+	public static final String COURT        = "court";
+	public static final String CURRENCY     = "currency";
+	public static final String CUSTOMER = "customer";
+	public static final String CUSTOMER_EMAIL = "customer_email";
+	public static final String CUSTOMER_NUMBER = "customer_number";
+	public static final String CUSTOMER_TAX_NUMBER = "customer_tax_number";
+	public static final String DEFAULT_HEADER = "default_header";
+	public static final String DEFAULT_FOOTER = "default_footer";
+	public static final String DEFAULT_MAIL = "type_mail_text";
+	public static final String DELIVERY = "delivery";
+	public static final String DELIVERY_DATE = "delivery_date";
+	public static final String DOCUMENT = "document";
+	public static final String DOCUMENT_ID = "document_id";
+	public static final String DOC_TYPE_ID = "document_type_id";
+	public static final String END_TIME     = "end_time";
+	public static final String FOOTER = "footer";
+	public static final String GROSS_SUM = "gross_sum";
+	public static final String HEAD = "head";
+	public static final String ITEM = "item";
+	public static final String ITEM_CODE = "item_code";
+	public static final String NET_PRICE = "net_price";
+	public static final String NET_SUM = "net_sum";
+	public static final String NEXT_TYPE = "next_type_id";
+	public static final String PHONE        = "phone";
+	public static final String POS = "pos";
+	public static final String POSITIONS = "positions";
+	public static final String PRICE = "single_price";
+	public static final String PRICE_FORMAT = "price_format";
+	public static final String START_TIME   = "start_time";
+	public static final String TASKS        = "tasks";
+	public static final String TAX_NUMBER   = "tax_number";
+	public static final String TAX          = "tax";
+	public static final String TAX_ID = "tax_id";
+	public static final String TEMPLATE_ID = "template_id";
+	public static final String TIME_ID = "time_id";
+	public static final String TYPE = "type";
+	public static final String TYPE_ID = "type_id";
+	public static final String TYPE_NUMBER = "type_number";
+	public static final String TYPE_PREFIX = "type_prefix";
+	public static final String TYPE_SUFFIX = "type_suffix";
+	public static final String UNIT = "unit";
+	public static final String UNIT_PRICE   = "unit_price";
+}