This PR adds the post reminder backend work.
We add a new API endpoint via which a user can set a reminder for a post. An ephemeral message will be sent down the line to let the user know about the action. And then after the time is over, the system admin bot will send a DM message to the user about the reminder post.
```release-note
We create a new config option MaxImageDecoderConcurrency which
indicates how many images can be decoded concurrently at once.
The default is -1 which means number of CPUs present.
This affects the total memory consumption of the server. The
maximum memory of a single image is dictated by MaxImageResolution * 24 bytes.
Therefore, a good rule of thumb to follow is that MaxImageResolution
* MaxImageDecoderConcurrency * 24 should be less then the allocated memory for
image decoding.
```
https://mattermost.atlassian.net/browse/MM-43733
This is more of a general refactor of the initialization
process which should allow us to pass services more
easily.
The changes are minimal to keep the scope limited.
For now, the objective is to pass the file service
to the Channels product. For that, it was required
to move some of the enterprise interfaces under Channels
from Server.
We also create a filestore field in the server to
avoid creating filestore reference every time
we make a filestore operation. This will be later
passed on to the Channels product.
Also removed an unnecessary test.
The test was working so far because we were creating
the filebackend every time for every request. But
we should go via UpdateConfig call which would fail,
were we to assign an invalid filestore name.
So we were actually testing for a different thing.
Therefore, removed the test.
```release-note
NONE
```
We create the basic boilerplate to pass services
to each product. The basic idea is to have a map
containing service names and the services.
The server will pass all services to all products.
But it is on the product, to choose what services
they will actually consume.
Each product will cast the received service to
an interface with the methods that product requires.
https://mattermost.atlassian.net/browse/MM-40813
```release-note
NONE
```
* 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
```
