refactor platform logic and add gasorder domain

backend/api/internal/models/gasorder_contract_revision.go

@@ -0,0 +1,24 @@
+package models
+
+import (
+	"time"
+
+	"git.apinb.com/bsm-sdk/core/database"
+)
+
+// GasorderContractRevision 对应 gasorder_contract_revision，保存唯一合同的不可变变更快照。
+type GasorderContractRevision struct {
+	Entity                        // 公共实体字段
+	GasorderContractID uint64     `gorm:"column:gasorder_contract_id;not null;index" json:"gasorder_contract_id"`                 // 合同自增主键
+	Action             string     `gorm:"column:action;type:varchar(32);not null;index" json:"action"`                            // 合同变更动作
+	ContractStatus     string     `gorm:"column:contract_status;type:varchar(32);not null" json:"contract_status"`                // 合同状态快照
+	EffectiveAt        time.Time  `gorm:"column:effective_at;type:timestamptz;not null" json:"effective_at"`                      // 生效时间快照
+	ExpiredAt          *time.Time `gorm:"column:expired_at;type:timestamptz" json:"expired_at"`                                   // 到期时间快照
+	OperatorIdentity   string     `gorm:"column:operator_identity;type:varchar(36);not null;default:''" json:"operator_identity"` // 操作人标识
+	OperatorName       string     `gorm:"column:operator_name;type:varchar(64);not null;default:''" json:"operator_name"`         // 操作人姓名快照
+	OccurredAt         time.Time  `gorm:"column:occurred_at;type:timestamptz;not null;index" json:"occurred_at"`                  // 发生时间
+	Reason             string     `gorm:"column:reason;type:text;not null;default:''" json:"reason"`                              // 变更原因
+}
+
+func init()                                               { database.AppendMigrate(&GasorderContractRevision{}) }
+func (table *GasorderContractRevision) TableName() string { return "gasorder_contract_revision" }