Implement GET channels endpoints for APIv4 (#5363)

* implement get channels endpoints and updated drivers and unittests

* removed channel deletion on tear down, removed manage permission on get channels endpoints, and updated utils to add constant channel length

* added constants for user, team and channel length, updated context to use the model functions

* make sure team name length should be less than the minimum length and revert underscore to team name validity

* changed post test condition from notfound to unauthorized

model/client4.go

@@ -72,6 +72,10 @@ func (c *Client4) GetTeamRoute(teamId string) string {
 	return fmt.Sprintf(c.GetTeamsRoute()+"/%v", teamId)
 }
 
+func (c *Client4) GetTeamByNameRoute(teamName string) string {
+	return fmt.Sprintf(c.GetTeamsRoute()+"/name/%v", teamName)
+}
+
 func (c *Client4) GetTeamMemberRoute(teamId, userId string) string {
 	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/members/%v", userId)
 }
@@ -84,6 +88,14 @@ func (c *Client4) GetChannelRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelsRoute()+"/%v", channelId)
 }
 
+func (c *Client4) GetChannelByNameRoute(channelName, teamId string) string {
+	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/channels/name/%v", channelName)
+}
+
+func (c *Client4) GetChannelByNameForTeamNameRoute(channelName, teamName string) string {
+	return fmt.Sprintf(c.GetTeamByNameRoute(teamName)+"/channels/name/%v", channelName)
+}
+
 func (c *Client4) GetChannelMembersRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelRoute(channelId) + "/members")
 }
@@ -444,6 +456,36 @@ func (c *Client4) CreateDirectChannel(userId1, userId2 string) (*Channel, *Respo
 	}
 }
 
+// GetChannel returns a channel based on the provided channel id string.
+func (c *Client4) GetChannel(channelId, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelRoute(channelId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByName returns a channel based on the provided channel name and team id strings.
+func (c *Client4) GetChannelByName(channelName, teamId string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameRoute(channelName, teamId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByNameForTeamName returns a channel based on the provided channel name and team name strings.
+func (c *Client4) GetChannelByNameForTeamName(channelName, teamName string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameForTeamNameRoute(channelName, teamName), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
 // GetChannelMembers gets a page of channel members.
 func (c *Client4) GetChannelMembers(channelId string, page, perPage int, etag string) (*ChannelMembers, *Response) {
 	query := fmt.Sprintf("?page=%v&per_page=%v", page, perPage)