refactor(extensions)!: refactor the extensions URLs and errors (#1636)

BREAKING CHANGE: The functionality provided by the mgmt endpoint has beed redesigned - see details below
BREAKING CHANGE: The API keys endpoint has been moved -  see details below
BREAKING CHANGE: The mgmt extension config has been removed - endpoint is now enabled by having both the search and the ui extensions enabled
BREAKING CHANGE: The API keys configuration has been moved from extensions to http>auth>apikey

mgmt and imagetrust extensions:
- separate the _zot/ext/mgmt into 3 separate endpoints: _zot/ext/auth, _zot/ext/notation, _zot/ext/cosign
- signature verification logic is in a separate `imagetrust` extension
- better hanling or errors in case of signature uploads: logging and error codes (more 400 and less 500 errors)
- add authz on signature uploads (and add a new middleware in common for this purpose)
- remove the mgmt extension configuration - it is now enabled if the UI and the search extensions are enabled

userprefs estension:
- userprefs are enabled if both search and ui extensions are enabled (as opposed to just search)

apikey extension is removed and logic moved into the api folder
- Move apikeys code out of pkg/extensions and into pkg/api
- Remove apikey configuration options from the extensions configuration and move it inside the http auth section
- remove the build label apikeys

other changes:
- move most of the logic adding handlers to the extensions endpoints out of routes.go and into the extensions files.
- add warnings in case the users are still using configurations with the obsolete settings for mgmt and api keys
- add a new function in the extension package which could be a single point of starting backgroud tasks for all extensions
- more clear methods for verifying specific extensions are enabled
- fix http methods paired with the UI handlers
- rebuild swagger docs

Signed-off-by: Andrei Aaron <aaaron@luxoft.com>

.github/workflows/codeql-analysis.yml

@@ -39,7 +39,7 @@ jobs:
         # https://docs.github.com/en/free-pro-team@latest/github/finding-security-vulnerabilities-and-errors-in-your-code/configuring-code-scanning#changing-the-languages-that-are-analyzed
     env:
       CGO_ENABLED: 0
-      GOFLAGS: "-tags=sync,search,scrub,metrics,userprefs,apikey,containers_image_openpgp"
+      GOFLAGS: "-tags=sync,search,scrub,metrics,userprefs,mgmt,imagetrust,containers_image_openpgp"
 
     steps:
     - name: Checkout repository

.github/workflows/golangci-lint.yaml

@@ -32,7 +32,7 @@ jobs:
 
           # Optional: golangci-lint command line arguments.
           # args: --issues-exit-code=0
-          args: --config ./golangcilint.yaml --enable-all --build-tags debug,needprivileges,sync,scrub,search,userprefs,metrics,containers_image_openpgp,lint,mgmt,apikey ./cmd/... ./pkg/...
+          args: --config ./golangcilint.yaml --enable-all --build-tags debug,needprivileges,sync,scrub,search,userprefs,metrics,containers_image_openpgp,lint,mgmt,imagetrust ./cmd/... ./pkg/...
 
           # Optional: show only new issues if it's a pull request. The default value is `false`.
           # only-new-issues: true