chore: enable forcetypeassert linter, fix issues (#38804)

Enable [`forcetypeassert`](https://github.com/gostaticanalysis/forcetypeassert)
linter to prevent unchecked type assertions. ~650 issues fixed, most
fixes were clean, some use `setting.PanicInDevOrTesting`.

The only behaviour changes are where code would previously send a 500 error
or panic, a 4xx error is now emitted.

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

tests/integration/api_httpsig_test.go

@@ -16,6 +16,7 @@ import (
 	"gitea.dev/tests"
 
 	"github.com/42wim/httpsig"
+	"github.com/stretchr/testify/require"
 	"golang.org/x/crypto/ssh"
 )
 
@@ -112,7 +113,9 @@ func TestHTTPSigCert(t *testing.T) {
 	keyID := "gitea"
 
 	// create our certificate signer using the ssh signer and our certificate
-	certSigner, err := ssh.NewCertSigner(pkcert.(*ssh.Certificate), sshSigner)
+	cert, ok := pkcert.(*ssh.Certificate)
+	require.True(t, ok)
+	certSigner, err := ssh.NewCertSigner(cert, sshSigner)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -121,7 +124,7 @@ func TestHTTPSigCert(t *testing.T) {
 	req = NewRequest(t, "GET", "/api/v1/admin/users")
 
 	// add our cert to the request
-	certString := base64.RawStdEncoding.EncodeToString(pkcert.(*ssh.Certificate).Marshal())
+	certString := base64.RawStdEncoding.EncodeToString(cert.Marshal())
 	req.SetHeader("x-ssh-certificate", certString)
 
 	signer, _, err := httpsig.NewSSHSigner(certSigner, httpsig.DigestSha512, []string{httpsig.RequestTarget, "(created)", "(expires)", "x-ssh-certificate"}, httpsig.Signature, 10)