[CT-3564] for deprecation - we should not support spaces in model names

[graciegoheen]

Housekeeping

• I am a maintainer of dbt-core

Short description

Spaces in model names was only ever supported incidentally & by accident. It’s never been documented.

• Having a space in a model name makes in impossible to select via --select on the model name because the argument gets split into pieces over spaces very early in the pipeline.
• Most warehouses will not like a table, or other object, with a space in its name.
• We may have to support table/view names with spaces for completeness on some platforms, but I we shouldn't support them in dbt's internal identifiers.

Acceptance criteria

We should mark spaces in model names:

• for deprecation (raise warning) in v1.8
• fully remove support in v1.9 (raise error)

Suggested Tests

1. test model name with space returns a warning in v1.8, error in v1.9

Impact to Other Teams

Impact: Exp and Adapters

Will backports be required?

No

Context

Impacting IDE team and file system.
How many customers are experiencing this warning?

[MichelleArk]

Notes from refinement:

• Let's consider adding a new ProjectFlag for this behaviour as well
• We should be able to use our existing deprecation tracking events to manage the deprecation lifecycle here. Some previous discussion: [Project Flags] Add telemetry to track the values of project-only flags #9518 (comment)

[QMalcolm]

@graciegoheen can, we create a separate ticket for the 1.9 to flip the flag?

[graciegoheen]

@QMalcolm Yep that's totally fine! We can add it to the 1.9 milestone

#9834

[FishtownBuildBot]

Opened a new issue in dbt-labs/docs.getdbt.com: dbt-labs/docs.getdbt.com#5275