Refactor SQL Generation Logic

* Created new `sqlgen` module to encapsulate sql generation
    * Broke SQLDialect inti new SQL generators for each statement type.
* Test refactor
    * Moved to a test case pattern to allow for quickly adding new test cases.

HISTORY.md

@@ -1,6 +1,13 @@
+## 8.4.0
+
+* Created new `sqlgen` module to encapsulate sql generation
+    * Broke SQLDialect inti new SQL generators for each statement type.
+* Test refactor
+    * Moved to a test case pattern to allow for quickly adding new test cases.
+
 ## v8.3.2
 
-* [FIXED] Data race during query factory initialisation [#133](https://github.com/doug-martin/goqu/issues/133) and [#136](https://github.com/doug-martin/goqu/issues/136) - [@o1egl](https://github.com/o1egl)
+* [FIXED] Data race during query factory initialization [#133](https://github.com/doug-martin/goqu/issues/133) and [#136](https://github.com/doug-martin/goqu/issues/136) - [@o1egl](https://github.com/o1egl)    
 
 ## 8.3.1
 

codecov.yml

@@ -0,0 +1,3 @@
+ignore:
+  - "**/mocks/**"         # glob accepted
+  - "mocks/**"         # glob accepted

delete_dataset.go

@@ -3,9 +3,12 @@ package goqu
 import (
 	"github.com/doug-martin/goqu/v8/exec"
 	"github.com/doug-martin/goqu/v8/exp"
+	"github.com/doug-martin/goqu/v8/internal/errors"
 	"github.com/doug-martin/goqu/v8/internal/sb"
 )
 
+var errBadFromArgument = errors.New("unsupported DeleteDataset#From argument, a string or identifier expression is required")
+
 type DeleteDataset struct {
 	dialect      SQLDialect
 	clauses      exp.DeleteClauses
@@ -108,7 +111,7 @@ func (dd *DeleteDataset) From(table interface{}) *DeleteDataset {
 	case string:
 		return dd.copy(dd.clauses.SetFrom(exp.ParseIdentifier(t)))
 	default:
-		panic("unsupported table type, a string or identifier expression is required")
+		panic(errBadFromArgument)
 	}
 }