(1.x) Base chat handler refactor for custom slash commands (#398)

[JasonWeill]

• Adds attributes, starts adding to subclasses

• Consistent syntax

• Help for all handlers

• Fix slash ID error

• Iterate through entry points

• Fix typo in call to select()

• Moves config to magics, modifies extensions to attempt to load classes

• [pre-commit.ci] auto fixes from pre-commit.com hooks

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• Moves config to proper location, improves error logging

• [pre-commit.ci] auto fixes from pre-commit.com hooks

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• WIP: Updates per feedback, adds custom handler

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• Removes redundant code, style fixes

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• Removes unnecessary custom message

• Instantiates class

• Validates slash ID

• [pre-commit.ci] auto fixes from pre-commit.com hooks

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• Consistent arguments to chat handlers

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• Refactors to avoid intentionally unused params

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• Updates docs, removes custom handler from source and config

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• Renames process_message to match base class

• Adds needed parameter that had been deleted

• Joins lines in contributor doc

• Removes natural language routing type, which is not yet used

• Update docs/source/developers/index.md

Co-authored-by: Piyush Jain [email protected]

• Update docs/source/developers/index.md

Co-authored-by: Piyush Jain [email protected]

• Update docs/source/developers/index.md

Co-authored-by: Piyush Jain [email protected]

• Revises per @3coins, avoids Latinism

• Removes Configurable, since we do not yet have configurable traits

• Uses Literal for validation

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Piyush Jain [email protected]
(cherry picked from commit 64e6daf)

[JasonWeill]

Closing in favor of #512.