API method to list all commits of a repository (#6408)

* Added API endpoint ListAllCommits (/repos/{owner}/{repo}/git/commits)

Signed-off-by: Mike Schwörer <mailport@mikescher.de>

* Fixed failing drone build

Signed-off-by: Mike Schwörer <mailport@mikescher.de>

* Implemented requested changes (PR reviews)

Signed-off-by: Mike Schwörer <mailport@mikescher.de>

* gofmt

Signed-off-by: Mike Schwörer <mailport@mikescher.de>

* Changed api route from "/repos/{owner}/{repo}/git/commits" to "/repos/{owner}/{repo}/commits"

* Removed unnecessary line

* better error message when git repo is empty

* make generate-swagger

* fixed removed return

* Update routers/api/v1/repo/commits.go

Co-Authored-By: Lauris BH <lauris@nix.lv>

* Update routers/api/v1/repo/commits.go

Co-Authored-By: Lauris BH <lauris@nix.lv>

* go fmt

* Refactored common code into ToCommit()

* made toCommit not exported

* added check for userCache == nil

modules/structs/miscellaneous.go

@@ -44,3 +44,9 @@ type MarkdownRender string
 type ServerVersion struct {
 	Version string `json:"version"`
 }
+
+// APIError is an api error with a message
+type APIError struct {
+	Message string `json:"message"`
+	URL     string `json:"url"`
+}