Support multiple Lovelace dashboards

[balloob]

Breaking change

Proposed change

Support multiple Lovelace dashboards. YAML only for this PR.

To do:

• Update docs
• Coordinate with @bramkragten if frontend changes for this are ok.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example entry for configuration.yaml:

# Example configuration.yaml
lovelace:
  dashboards:
    bla:
      mode: yaml
      filename: bla.yaml
      sidebar:  # Optional
        title: Make it rain
        icon: mdi:cash-100
    generated:
      mode: yaml
      # Same behavior as with default. If file doesn't exist we generate one.
      filename: notexist.yaml

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
• 🥈 Silver
• 🥇 Gold
• 🏆 Platinum

[probot-home-assistant]

Hey there @home-assistant/frontend, mind taking a look at this pull request as its been labeled with a integration (lovelace) you are listed as a codeowner for? Thanks!

[probot-home-assistant]

Hey there @home-assistant/frontend, mind taking a look at this pull request as its been labeled with a integration (frontend) you are listed as a codeowner for? Thanks!

[codecov]

Codecov Report

Merging #32134 into dev will increase coverage by 0.02%.
The diff coverage is 94.75%.

@@            Coverage Diff             @@
##              dev   #32134      +/-   ##
==========================================
+ Coverage   94.73%   94.75%   +0.02%     
==========================================
  Files         767      772       +5     
  Lines       55505    55857     +352     
==========================================
+ Hits        52580    52928     +348     
- Misses       2925     2929       +4

Impacted Files	Coverage Δ
...eassistant/components/websocket_api/permissions.py	100% <100%> (ø)	⬆️
homeassistant/helpers/config_validation.py	96.01% <100%> (ø)	⬆️
homeassistant/helpers/collection.py	95.81% <100%> (+0.22%)	⬆️
homeassistant/components/lovelace/const.py	100% <100%> (ø)
homeassistant/components/lovelace/websocket.py	93.47% <93.47%> (ø)
homeassistant/components/lovelace/dashboard.py	93.75% <93.75%> (ø)
homeassistant/components/lovelace/resources.py	94.11% <94.11%> (ø)
...meassistant/components/mqtt/vacuum/schema_state.py	91.13% <0%> (-0.59%)	⬇️
homeassistant/components/twitch/sensor.py	96.7% <0%> (-0.04%)	⬇️
homeassistant/components/rflink/light.py	100% <0%> (ø)	⬆️
... and 62 more

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[balloob]

This is not something that the collection should be aware off. We should pop this out before it gets here.

[balloob]

This is not something that the collection should be aware off. We should pop this out before it gets here.

[codecov-io]

Codecov Report

Merging #32134 into dev will increase coverage by 0.02%.
The diff coverage is 94.75%.

@@            Coverage Diff             @@
##              dev   #32134      +/-   ##
==========================================
+ Coverage   94.73%   94.75%   +0.02%     
==========================================
  Files         767      772       +5     
  Lines       55505    55861     +356     
==========================================
+ Hits        52580    52930     +350     
- Misses       2925     2931       +6

Impacted Files	Coverage Δ
...eassistant/components/websocket_api/permissions.py	100% <100%> (ø)	⬆️
homeassistant/helpers/config_validation.py	96.01% <100%> (ø)	⬆️
homeassistant/helpers/collection.py	95.81% <100%> (+0.22%)	⬆️
homeassistant/components/lovelace/const.py	100% <100%> (ø)
homeassistant/components/lovelace/websocket.py	93.47% <93.47%> (ø)
homeassistant/components/lovelace/dashboard.py	93.75% <93.75%> (ø)
homeassistant/components/lovelace/resources.py	94.11% <94.11%> (ø)
...istant/components/google_assistant/report_state.py	83.33% <0%> (-1.67%)	⬇️
homeassistant/components/alexa/state_report.py	83.63% <0%> (-0.63%)	⬇️
...meassistant/components/mqtt/vacuum/schema_state.py	91.13% <0%> (-0.59%)	⬇️
... and 64 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9801810...3824da9. Read the comment docs.