* Move enterprise features under Channels
We move the EE features which are Channels related.
While here, we also move some code under *Server.Start()
from NewServer.
```release-note
NONE
```
* move saml and ldap back to server
```release-note
NONE
```
* fix test
```release-note
NONE
```
* try again
```release-note
NONE
```
* Move pluginCommands into Channels
We move pluginCommands, pluginCommandsLock
into Channels.
We also move the plugin related route handlers
under Channels and move the init code under
NewChannels. To achieve this, the router initialization
is bumped up.
Along with it, we clean up some App methods
which were just wrappers over Channel methods.
Instead, we call the Channel method directly
to make things more readable and easy to understand.
```release-note
NONE
```
* fix tests
```release-note
NONE
```
* Move plugins under Channels
We move all plugin related fields under *Channels.
This essentially migrates several methods from being under
*Server to under *Channels.
We also move the plugin startup and shutdown code
to be under Channels.Start and Channels.Shutdown.
While here, we remove the getPluginPublicKeyFiles
method which was a one-line method which uselessly
returned an error.
Lastly, we fix the product initialization order which
was incorrect previously. Products are dependent on
the main server.
So startup should be products -> server.
And shutdown should be server -> products.
```release-note
NONE
```
* Added app layer
```release-note
NONE
```
* Incorporate suggestions
```release-note
NONE
```
* Move some more atomic values under Channels
The following fields were moved:
```
asymmetricSigningKey atomic.Value
clientConfig atomic.Value
clientConfigHash atomic.Value
limitedClientConfig atomic.Value
```
And also moved the initialization order from NewServer
to Channels.Start to better reflect the order of things.
Removed AsymmetricSigningKey from ConfigService
as it was no longer used.
Removed calling regenerateClientConfig during startup explicitly
because it was anyways called from ensureAsymmetricSigningKey.
https://community-daily.mattermost.com/boards/workspace/zyoahc9uapdn3xdptac6jb69ic/285b80a3-257d-41f6-8cf4-ed80ca9d92e5/495cdb4d-c13a-4992-8eb9-80cfee2819a4?c=87df1e15-588e-49ff-8bd1-ffa9651b8c82
```release-note
NONE
```
* Fix lint error
```release-note
NONE
```
* Move Channels into App
In this PR, we make Channels as part of App
instead of Server. This is part of the transition period
of moving fields from Server to Channels.
For now, Channels contains Server. So the hierarchy is
App -> Channels -> Server.
And as a first step, we also move httpService to Channels.
```release-note
NONE
```
* Fixing another test
```release-note
NONE
```
* new method
```release-note
NONE
```
* Creating empty Channels shell
This is the first step in moving to a product-based
isolated architecture.
For now, Channels is empty and does not contain anything.
Next step is to change App to contain Channels instead
of Server. Some of the initialization code in NewServer
would need to be moved inside NewChannels.
This would complete the full pass-through mode of accessing
everything.
The last step would be to gradually move Channels related
fields from Server into Channels, keeping Server to be
just the global level struct.
```release-note
NONE
```
* fix vet failure
```release-note
NONE
```
