Remove GetByBean method because sometimes it's danger when query condition parameter is zero and also introduce new generic methods (#28220)

The function `GetByBean` has an obvious defect that when the fields are
empty values, it will be ignored. Then users will get a wrong result
which is possibly used to make a security problem.

To avoid the possibility, this PR removed function `GetByBean` and all
references.
And some new generic functions have been introduced to be used.

The recommand usage like below.

```go
// if query an object according id
obj, err := db.GetByID[Object](ctx, id)
// query with other conditions
obj, err := db.Get[Object](ctx, builder.Eq{"a": a, "b":b})
```

3 files changed, 59 insertions, 11 deletions

diff --git a/models/db/context.go b/models/db/context.go
index 45765ef7d3..7b739f7e9f 100644
--- a/models/db/context.go
+++ b/models/db/context.go
@@ -173,9 +173,44 @@ func Exec(ctx context.Context, sqlAndArgs ...any) (sql.Result, error) {
 	return GetEngine(ctx).Exec(sqlAndArgs...)
 }
 
-// GetByBean filled empty fields of the bean according non-empty fields to query in database.
-func GetByBean(ctx context.Context, bean any) (bool, error) {
-	return GetEngine(ctx).Get(bean)
+func Get[T any](ctx context.Context, cond builder.Cond) (object *T, exist bool, err error) {
+	if !cond.IsValid() {
+		return nil, false, ErrConditionRequired{}
+	}
+
+	var bean T
+	has, err := GetEngine(ctx).Where(cond).NoAutoCondition().Get(&bean)
+	if err != nil {
+		return nil, false, err
+	} else if !has {
+		return nil, false, nil
+	}
+	return &bean, true, nil
+}
+
+func GetByID[T any](ctx context.Context, id int64) (object *T, exist bool, err error) {
+	var bean T
+	has, err := GetEngine(ctx).ID(id).NoAutoCondition().Get(&bean)
+	if err != nil {
+		return nil, false, err
+	} else if !has {
+		return nil, false, nil
+	}
+	return &bean, true, nil
+}
+
+func Exist[T any](ctx context.Context, cond builder.Cond) (bool, error) {
+	if !cond.IsValid() {
+		return false, ErrConditionRequired{}
+	}
+
+	var bean T
+	return GetEngine(ctx).Where(cond).NoAutoCondition().Exist(&bean)
+}
+
+func ExistByID[T any](ctx context.Context, id int64) (bool, error) {
+	var bean T
+	return GetEngine(ctx).ID(id).NoAutoCondition().Exist(&bean)
 }
 
 // DeleteByBean deletes all records according non-empty fields of the bean as conditions.
@@ -264,8 +299,3 @@ func inTransaction(ctx context.Context) (*xorm.Session, bool) {
 		return nil, false
 	}
 }
-
-func Exists[T any](ctx context.Context, opts FindOptions) (bool, error) {
-	var bean T
-	return GetEngine(ctx).Where(opts.ToConds()).Exist(&bean)
-}
diff --git a/models/db/error.go b/models/db/error.go
index 665e970e17..f601a15c01 100644
--- a/models/db/error.go
+++ b/models/db/error.go
@@ -72,3 +72,21 @@ func (err ErrNotExist) Error() string {
 func (err ErrNotExist) Unwrap() error {
 	return util.ErrNotExist
 }
+
+// ErrConditionRequired represents an error which require condition.
+type ErrConditionRequired struct{}
+
+// IsErrConditionRequired checks if an error is an ErrConditionRequired
+func IsErrConditionRequired(err error) bool {
+	_, ok := err.(ErrConditionRequired)
+	return ok
+}
+
+func (err ErrConditionRequired) Error() string {
+	return "condition is required"
+}
+
+// Unwrap unwraps this as a ErrNotExist err
+func (err ErrConditionRequired) Unwrap() error {
+	return util.ErrInvalidArgument
+}
diff --git a/models/db/iterate_test.go b/models/db/iterate_test.go
index 5362f34075..0f6ba2cc94 100644
--- a/models/db/iterate_test.go
+++ b/models/db/iterate_test.go
@@ -31,11 +31,11 @@ func TestIterate(t *testing.T) {
 	assert.EqualValues(t, cnt, repoUnitCnt)
 
 	err = db.Iterate(db.DefaultContext, nil, func(ctx context.Context, repoUnit *repo_model.RepoUnit) error {
-		reopUnit2 := repo_model.RepoUnit{ID: repoUnit.ID}
-		has, err := db.GetByBean(ctx, &reopUnit2)
+		has, err := db.ExistByID[repo_model.RepoUnit](ctx, repoUnit.ID)
 		if err != nil {
 			return err
-		} else if !has {
+		}
+		if !has {
 			return db.ErrNotExist{Resource: "repo_unit", ID: repoUnit.ID}
 		}
 		assert.EqualValues(t, repoUnit.RepoID, repoUnit.RepoID)