feat: ESPI 4.0 Schema Compliance - Phase 0.5: OAuth and Common Domain Enums (#109)

* feat: ESPI 4.0 Schema Compliance - Phase 0.5: OAuth and Common Domain Enums

Implements OAuth 2.0 and common domain enumerations from espi.xsd with
proper JAXB/Jakarta XML binding annotations and comprehensive documentation.

OAuth Enums (String values):
- GrantType (3 values) - OAuth 2.0 grant types (authorization_code, client_credentials, refresh_token)
- TokenType (1 value) - OAuth 2.0 token types (Bearer)
- OAuthError (13 values) - OAuth 2.0 error codes per RFC 6749
- ResponseType (1 value) - OAuth 2.0 response types (code)
- TokenEndPointMethod (1 value) - Token endpoint authentication methods

Common Enums (int values):
- Currency (14 values) - ISO 4217 currency codes (USD, EUR, GBP, etc.)
- StatusCode (14 values) - HTTP status codes for transaction status

Refactoring:
- Moved enums from domain/common/ to domain/common/enums/ package
- Deleted old enum files (GrantType, TokenType, OAuthError, ResponseType)
- Updated all imports in entity and test files
- Added wildcard import for domain/common/enums in affected files
- Updated tests to use ESPI 4.0 compliant ResponseType.CODE (removed non-standard TOKEN)

All enums include:
- Apache License 2.0 header (copyright 2025 Green Button Alliance, Inc.)
- JAXB/Jakarta XML binding annotations (@XmlType, @XmlEnum, @XmlEnumValue)
- getValue() and fromValue() methods with IllegalArgumentException for invalid values
- Comprehensive Javadoc from XSD documentation with line numbers
- Type-safe enum constants (String for OAuth, int for Currency/StatusCode)

Total enum values in batch: 47
Per ESPI 4.0 specification (NAESB REQ.21)

All tests: 781/781 passed ✓
- Unit tests: 638/638 passed
- Integration tests: 143/143 passed (with Docker/TestContainers)

Related to #101

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* fix: Update import in ModernAuthorizationController for relocated enums

Updates import statements in openespi-thirdparty ModernAuthorizationController
to use new enum package location (domain/common/enums).

Fixes compilation error in openespi-thirdparty module.

---------

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: dfcoffin

openespi-common/src/main/java/org/greenbuttonalliance/espi/common/domain/common/GrantType.java

@@ -0,0 +1,150 @@
+/*
+ * Copyright (c) 2025 Green Button Alliance, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.greenbuttonalliance.espi.common.domain.common.enums;
+
+import jakarta.xml.bind.annotation.XmlEnum;
+import jakarta.xml.bind.annotation.XmlEnumValue;
+import jakarta.xml.bind.annotation.XmlType;
+
+/**
+ * Enumeration for Currency values.
+ *
+ * Code for the currency for costs associated with this ReadingType.
+ * The valid values per the standard are defined in CurrencyCode.
+ * Per ESPI 4.0 espi.xsd lines 2101-2195.
+ */
+@XmlType(name = "Currency", namespace = "http://naesb.org/espi")
+@XmlEnum
+public enum Currency {
+
+    /**
+     * US dollar.
+     * XSD value: 840 (line 2108)
+     */
+    @XmlEnumValue("840")
+    USD(840),
+
+    /**
+     * European euro.
+     * XSD value: 978 (line 2114)
+     */
+    @XmlEnumValue("978")
+    EUR(978),
+
+    /**
+     * Australian dollar.
+     * XSD value: 36 (line 2120)
+     */
+    @XmlEnumValue("36")
+    AUD(36),
+
+    /**
+     * Canadian dollar.
+     * XSD value: 124 (line 2126)
+     */
+    @XmlEnumValue("124")
+    CAD(124),
+
+    /**
+     * Swiss francs.
+     * XSD value: 756 (line 2132)
+     */
+    @XmlEnumValue("756")
+    CHF(756),
+
+    /**
+     * Chinese yuan renminbi.
+     * XSD value: 156 (line 2138)
+     */
+    @XmlEnumValue("156")
+    CNY(156),
+
+    /**
+     * Danish crown.
+     * XSD value: 208 (line 2144)
+     */
+    @XmlEnumValue("208")
+    DKK(208),
+
+    /**
+     * British pound.
+     * XSD value: 826 (line 2150)
+     */
+    @XmlEnumValue("826")
+    GBP(826),
+
+    /**
+     * Japanese yen.
+     * XSD value: 392 (line 2156)
+     */
+    @XmlEnumValue("392")
+    JPY(392),
+
+    /**
+     * Norwegian crown.
+     * XSD value: 578 (line 2162)
+     */
+    @XmlEnumValue("578")
+    NOK(578),
+
+    /**
+     * Russian ruble.
+     * XSD value: 643 (line 2168)
+     */
+    @XmlEnumValue("643")
+    RUB(643),
+
+    /**
+     * Swedish crown.
+     * XSD value: 752 (line 2174)
+     */
+    @XmlEnumValue("752")
+    SEK(752),
+
+    /**
+     * India rupees.
+     * XSD value: 356 (line 2180)
+     */
+    @XmlEnumValue("356")
+    INR(356),
+
+    /**
+     * Another type of currency.
+     * XSD value: 0 (line 2186)
+     */
+    @XmlEnumValue("0")
+    OTHER(0);
+
+    private final int value;
+
+    Currency(int value) {
+        this.value = value;
+    }
+
+    public int getValue() {
+        return value;
+    }
+
+    public static Currency fromValue(int value) {
+        for (Currency kind : Currency.values()) {
+            if (kind.value == value) {
+                return kind;
+            }
+        }
+        throw new IllegalArgumentException("Invalid Currency value: " + value);
+    }
+}