backtester: custom strategy plugins (#989)

* Adds custom strategy

* docs and structure

* docs

* rn

* Documents plugins, adds custom strat config

* mini fixes. Fleshes strategy test

* docgen

* Updates plugins to allow for multiple strategies to be loaded

* docs

* docs regen

* fix doc accuracy

* why did I add the word custom?

cmd/documentation/backtester_templates/backtester_plugins_readme.tmpl

@@ -0,0 +1,36 @@
+{{define "backtester plugins" -}}
+{{template "backtester-header" .}}
+## {{.CapitalName}} package overview
+
+Golang Plugins are supported by the GoCryptoTrader Backtester. At present, only custom strategies are supported.
+
+Please read the Golang documentation on [plugins](https://golang.org/pkg/plugin/) for more information.
+
+## Building Golang Plugins
+
+### Windows
+Plugin support is not yet available for Windows. However, you can still build via WSL. See below for instructions on a basic setup for WSL. Once completed, follow the instructions for Linux.
+#### WSL Setup
+The following is a basic setup for WSL: [here](https://pureinfotech.com/install-wsl-windows-11/)
+
+### Linux, macOS & WSL
+A plugin is a Go main package with exported functions and variables that has been built with:
+
+```bash
+go build -buildmode=plugin
+```
+
+This outputs a file named `{{.Name}}.so` which can be loaded by the backtester. At present, only custom strategies can be loaded. See [here](/strategies/example/README.md) for more information on building custom strategies via plugins.
+
+You must ensure that the plugin is built with the same version of code as the GoCryptoTrader Backtester. Otherwise the plugin will refuse to load.
+
+
+
+#### Installing Golang in WSL
+See the following for instructions on installing Golang in WSL: [here](https://ao.ms/how-to-install-golang-on-wsl-wsl2/)
+
+
+### Please click GoDocs chevron above to view current GoDoc information for this package
+{{template "contributions"}}
+{{template "donations" .}}
+{{end}}

cmd/documentation/backtester_templates/backtester_plugins_strategies_example_readme.tmpl

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+{{define "backtester plugins strategies example" -}}
+{{template "backtester-header" .}}
+## {{.CapitalName}} package overview
+
+This is a custom strategy for the GoCryptoTrader Backtester. It is a simple example of a strategy that trades a pair of assets and is used to highlight how strategies can be loaded from external sources.
+
+### Designing a strategy
+- File must contain `main` package.
+- Custom strategy plugins must adhere to the strategy.Handler interface. See the [strategy.Handler interface documentation](./backtester/eventhandlers/strategies/README.md) for more information.
+- Must contain function `func GetStrategies() []strategy.Handler` to return a slice of implemented `strategy.Handler`.
+   - If only using one custom strategy, can simply `return []strategy.Handler{&customStrategy{}}`.
+
+### Building
+See [here](./backtester/plugins/README.md) for details on how to build the plugin file.
+
+### Running
+Plugins can only be loaded via Linux, macOS and WSL. Windows itself is not supported.
+
+To run this strategy you will need to use the following flags when running the GoCryptoTrader Backtester:
+
+```bash
+./backtester -strategypluginpath="path/to/strategy/example.so"
+```
+
+To run this specific example strategy, use:
+
+```bash
+./backtester --strategypluginpath="./plugins/strategies/example/example.so"
+```
+
+Upon startup, the GoCryptoTrader Backtester will load the strategy and run it for all events.
+
+
+### Please click GoDocs chevron above to view current GoDoc information for this package
+{{template "contributions"}}
+{{template "donations" .}}
+{{end}}

cmd/documentation/backtester_templates/backtester_plugins_strategies_readme.tmpl

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+{{define "backtester plugins strategies" -}}
+{{template "backtester-header" .}}
+## {{.CapitalName}} package overview
+
+### Designing a strategy
+- File must contain `main` package
+- Custom strategy plugins must adhere to the strategy.Handler interface. See the [strategy.Handler interface documentation](./backtester/eventhandlers/strategies/README.md) for more information.
+- Must contain function `func GetStrategies() []strategy.Handler` to return a slice of implemented `strategy.Handler`.
+   - If only using one custom strategy, can simply `return []strategy.Handler{&customStrategy{}}`.
+
+
+### Building
+See [here](./backtester/plugins/README.md) for details on how to build the plugin file.
+
+### Running
+Plugins can only be loaded via Linux, macOS and WSL. Windows itself is not supported.
+
+To run a strategy you will need to use the following flags when running the GoCryptoTrader Backtester:
+
+```bash
+./backtester -strategypluginpath="path/to/strategy/example.so"
+```
+
+Upon startup, the GoCryptoTrader Backtester will load the strategy and run it for all events.
+
+
+### Please click GoDocs chevron above to view current GoDoc information for this package
+{{template "contributions"}}
+{{template "donations" .}}
+{{end}}