Simplify Gothic to use our session store instead of creating a different store (#17507)

* Simplify Gothic to use our session store instead of creating a different store

We have been using xormstore to provide a separate session store for our OAuth2 logins
however, this relies on using gorilla context and some doubling of our session storing.
We can however, simplify and simply use our own chi-based session store. Thus removing
a cookie and some of the weirdness with missing contexts.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* as per review

Signed-off-by: Andrew Thornton <art27@cantab.net>

* as per review

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Handle MaxTokenLength

Signed-off-by: Andrew Thornton <art27@cantab.net>

* oops

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: Lauris BH <lauris@nix.lv>

go.mod

@@ -55,10 +55,9 @@ require (
 	github.com/golang/snappy v0.0.4 // indirect
 	github.com/google/go-github/v39 v39.2.0
 	github.com/google/uuid v1.2.0
-	github.com/gorilla/context v1.1.1
 	github.com/gorilla/feeds v1.1.1
 	github.com/gorilla/mux v1.8.0 // indirect
-	github.com/gorilla/sessions v1.2.1 // indirect
+	github.com/gorilla/sessions v1.2.1
 	github.com/hashicorp/go-cleanhttp v0.5.2 // indirect
 	github.com/hashicorp/go-retryablehttp v0.7.0 // indirect
 	github.com/hashicorp/go-version v1.3.1
@@ -73,7 +72,6 @@ require (
 	github.com/klauspost/compress v1.13.1
 	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
 	github.com/klauspost/pgzip v1.2.5 // indirect
-	github.com/lafriks/xormstore v1.4.0
 	github.com/lib/pq v1.10.2
 	github.com/lunny/dingtalk_webhook v0.0.0-20171025031554-e3534c89ef96
 	github.com/markbates/goth v1.68.0