Update Mattermost to 5.37.0

Update to latest image from IB.

Upstream changelog to verify no breaking changes/what is needed to switch images: https://docs.mattermost.com/administration/changelog.html

Definition of Done:

• Image version updated in chart/values.yaml
• Chart version bumped bb.x -> bb.y
• Changelog entry added, note the update to image, any additional updates
• Clean install tested and validated working (see things to test)
• Upgrade tested and validated working (install newest tagged release, send some chats/change settings, upgrade to your branch, validate things persisted, then run through things to test)
• Pipeline passing on package MR
• Package MR merged and new MM release tagged
• BB MR opened, pipeline passing
• BB MR merged

Things to test:

• Test that signing up works and you can chat, validate that chats stick around and are persistent
• Test that logging out/in works with your account
• From the system console, go to file storage and test the connection, validate it succeeds. Also try to upload a profile picture.
• Install with dev SSO values (https://repo1.dso.mil/platform-one/big-bang/bigbang/-/blob/master/chart/dev-sso-values.yaml#L82) and validate you can login via SSO
• Install with monitoring enabled and enterprise enabled, from the system console start a trial, go to prometheus and validate that the target for Mattermost shows as up

added to epic &67 (closed)

added mattermost priority7 + 1 deleted label

set weight to 2

changed iteration to Big Bang Iterations Jul 27, 2021 - Aug 9, 2021

changed milestone to %1.15.0

changed iteration to Big Bang Iterations Aug 10, 2021 - Aug 23, 2021

assigned to @BrandenCobb

marked the checklist item Image version updated in chart/values.yaml as completed

marked the checklist item Chart version bumped bb.x -> bb.y as completed

marked the checklist item Changelog entry added, note the update to image, any additional updates as completed

marked the checklist item Clean install tested and validated working (see things to test) as completed

marked the checklist item Pipeline passing on package MR as completed

marked the checklist item Upgrade tested and validated working (install newest tagged release, send some chats/change settings, upgrade to your branch, validate things persisted, then run through things to test) as completed

changed milestone to %1.14.0

changed iteration to Big Bang Iterations Jul 27, 2021 - Aug 9, 2021

added statusdoing label

This will be part of this MR:

https://repo1.dso.mil/platform-one/big-bang/bigbang/-/merge_requests/685

mentioned in merge request !685 (merged)

added statusreview label and removed statusdoing label

marked the checklist item Package MR merged and new MM release tagged as completed

marked the checklist item BB MR opened, pipeline passing as completed

changed milestone to %1.15.0

changed iteration to Big Bang Iterations Aug 10, 2021 - Aug 23, 2021

closed with merge request !685 (merged)

mentioned in commit 600f6fa4

removed statusreview label