Added migration identifier to all migration related logs

[Danil-Grigorev]

{"level":"info","ts":1567791963.0011566,"logger":"migration|z695n","msg":"[RUN]","migration":"28ea12a0-d0ce-11e9-9a4f-6399de957532","stage":true,"phase":"EnsureStagePods"}
{"level":"info","ts":1567791964.275831,"logger":"migration|z695n","msg":"Stage pod created.","migration":"28ea12a0-d0ce-11e9-9a4f-6399de957532","ns":"mssql-persistent","name":"mssql-deployment-1-zx8sv-stage"}
{"level":"error","ts":1567791964.5248604,"logger":"migration|z695n","msg":"","migration":"28ea12a0-d0ce-11e9-9a4f-6399de957532","error":"Pod \"mssql-deployment-1-zx8sv\" is invalid: spec: Forbidden: pod updates may not change fields other than `spec.containers[*].image`, `spec.initContainers[*].image`, `spec.activeDeadlineSeconds` or `spec.toleratio

Added migration field to simplify the selection of migration related log entries. This could help filtering logs in the UI.

[jortel]

This can probably go on (1) line now as well.

[jortel]

Seems reasonable.

[jortel]

@Danil-Grigorev I have a branch with some logger fixes: #308 and added SetValues() so it's not necessary to modify the Logger internals (Real). Please consider reviewing and basing your PR on this instead.

[jortel]

Looking at:

"Migration [RUN]","migration":"foo"

The word Migration seems kind of redundant with the migration keyword. Perhaps the logging in the Task should just be:

"RUN","migration":"foo"

I still like the all CAPS because it makes those entries easier to pick out.

Thoughts?

[Danil-Grigorev]

I'll include all the changes on top of the #308. Agree with all suggestions.

[djwhatle]

MigMigration name alone (without namespace) isn't necessarily unique, but since we expect all MigMigrations to be created in the same namespace I think this will work well enough for log filtering purposes without adding excessive clutter to the logs.

[sseago]

We need to be careful assuming all migmigrations are in the same namespace. If it's just for logging purposes, it's probably OK, but nothing prevents CLI users from putting migrations in whatever namespaces they want to use. I've tested this and migrations work fine, even if created in a different namespace.