Decouple the different contexts from each other (#24786)

Replace #16455

Close #21803

Mixing different Gitea contexts together causes some problems:

1. Unable to respond proper content when error occurs, eg: Web should
respond HTML while API should respond JSON
2. Unclear dependency, eg: it's unclear when Context is used in
APIContext, which fields should be initialized, which methods are
necessary.


To make things clear, this PR introduces a Base context, it only
provides basic Req/Resp/Data features.

This PR mainly moves code. There are still many legacy problems and
TODOs in code, leave unrelated changes to future PRs.

routers/api/v1/repo/hook_test.go

@@ -9,7 +9,6 @@ import (
 
 	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/models/webhook"
-	"code.gitea.io/gitea/modules/context"
 	"code.gitea.io/gitea/modules/test"
 
 	"github.com/stretchr/testify/assert"
@@ -18,12 +17,12 @@ import (
 func TestTestHook(t *testing.T) {
 	unittest.PrepareTestEnv(t)
 
-	ctx := test.MockContext(t, "user2/repo1/wiki/_pages")
+	ctx := test.MockAPIContext(t, "user2/repo1/wiki/_pages")
 	ctx.SetParams(":id", "1")
 	test.LoadRepo(t, ctx, 1)
 	test.LoadRepoCommit(t, ctx)
 	test.LoadUser(t, ctx, 2)
-	TestHook(&context.APIContext{Context: ctx, Org: nil})
+	TestHook(ctx)
 	assert.EqualValues(t, http.StatusNoContent, ctx.Resp.Status())
 
 	unittest.AssertExistsAndLoadBean(t, &webhook.HookTask{