Add Webhook authorization header (#20926)

_This is a different approach to #20267, I took the liberty of adapting
some parts, see below_

## Context

In some cases, a weebhook endpoint requires some kind of authentication.
The usual way is by sending a static `Authorization` header, with a
given token. For instance:

- Matrix expects a `Bearer <token>` (already implemented, by storing the
header cleartext in the metadata - which is buggy on retry #19872)
- TeamCity #18667
- Gitea instances #20267
- SourceHut https://man.sr.ht/graphql.md#authentication-strategies (this
is my actual personal need :)

## Proposed solution

Add a dedicated encrypt column to the webhook table (instead of storing
it as meta as proposed in #20267), so that it gets available for all
present and future hook types (especially the custom ones #19307).

This would also solve the buggy matrix retry #19872.

As a first step, I would recommend focusing on the backend logic and
improve the frontend at a later stage. For now the UI is a simple
`Authorization` field (which could be later customized with `Bearer` and
`Basic` switches):


![2022-08-23-142911](https://user-images.githubusercontent.com/3864879/186162483-5b721504-eef5-4932-812e-eb96a68494cc.png)

The header name is hard-coded, since I couldn't fine any usecase
justifying otherwise.

## Questions

- What do you think of this approach? @justusbunsi @Gusted @silverwind 
- ~~How are the migrations generated? Do I have to manually create a new
file, or is there a command for that?~~
- ~~I started adding it to the API: should I complete it or should I
drop it? (I don't know how much the API is actually used)~~

## Done as well:

- add a migration for the existing matrix webhooks and remove the
`Authorization` logic there


_Closes #19872_

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Gusted <williamzijl7@hotmail.com>
Co-authored-by: delvh <dev.lh@web.de>

3 files changed, 21 insertions, 4 deletions

diff --git a/templates/repo/settings/webhook/matrix.tmpl b/templates/repo/settings/webhook/matrix.tmpl
index 8edab870cf..d3ab5588bf 100644
--- a/templates/repo/settings/webhook/matrix.tmpl
+++ b/templates/repo/settings/webhook/matrix.tmpl
@@ -10,10 +10,6 @@
 			<label for="room_id">{{.locale.Tr "repo.settings.matrix.room_id"}}</label>
 			<input id="room_id" name="room_id" type="text" value="{{.MatrixHook.Room}}" required>
 		</div>
-		<div class="required field {{if .Err_AccessToken}}error{{end}}">
-			<label for="access_token">{{.locale.Tr "repo.settings.matrix.access_token"}}</label>
-			<input id="access_token" name="access_token" type="text" value="{{.MatrixHook.AccessToken}}" required>
-		</div>
 		<div class="field">
 			<label>{{.locale.Tr "repo.settings.matrix.message_type"}}</label>
 				<div class="ui selection dropdown">
diff --git a/templates/repo/settings/webhook/settings.tmpl b/templates/repo/settings/webhook/settings.tmpl
index 1543bef6ca..42bc144b6f 100644
--- a/templates/repo/settings/webhook/settings.tmpl
+++ b/templates/repo/settings/webhook/settings.tmpl
@@ -248,6 +248,15 @@
 	<span class="help">{{.locale.Tr "repo.settings.branch_filter_desc" | Str2html}}</span>
 </div>
 
+<!-- Authorization Header -->
+<div class="field{{if eq .HookType "matrix"}} required{{end}}">
+	<label for="authorization_header">{{.locale.Tr "repo.settings.authorization_header"}}</label>
+	<input id="authorization_header" name="authorization_header" type="text" value="{{.Webhook.HeaderAuthorization}}"{{if eq .HookType "matrix"}} placeholder="Bearer $access_token" required{{end}}>
+	{{if ne .HookType "matrix"}}{{/* Matrix doesn't make the authorization optional but it is implied by the help string, should be changed.*/}}
+		<span class="help">{{.locale.Tr "repo.settings.authorization_header_desc" "<code>Bearer token123456</code>, <code>Basic YWxhZGRpbjpvcGVuc2VzYW1l</code>" | Str2html}}</span>
+	{{end}}
+</div>
+
 <div class="ui divider"></div>
 
 <div class="inline field">
diff --git a/templates/swagger/v1_json.tmpl b/templates/swagger/v1_json.tmpl
index 94fb67ab44..229e219064 100644
--- a/templates/swagger/v1_json.tmpl
+++ b/templates/swagger/v1_json.tmpl
@@ -14448,6 +14448,10 @@
           "default": false,
           "x-go-name": "Active"
         },
+        "authorization_header": {
+          "type": "string",
+          "x-go-name": "AuthorizationHeader"
+        },
         "branch_filter": {
           "type": "string",
           "x-go-name": "BranchFilter"
@@ -15437,6 +15441,10 @@
           "type": "boolean",
           "x-go-name": "Active"
         },
+        "authorization_header": {
+          "type": "string",
+          "x-go-name": "AuthorizationHeader"
+        },
         "branch_filter": {
           "type": "string",
           "x-go-name": "BranchFilter"
@@ -16544,6 +16552,10 @@
           "type": "boolean",
           "x-go-name": "Active"
         },
+        "authorization_header": {
+          "type": "string",
+          "x-go-name": "AuthorizationHeader"
+        },
         "config": {
           "type": "object",
           "additionalProperties": {