Add README

README.md

@@ -13,11 +13,70 @@ simplified and only works with signed APIs.
 
 ## Configuration
 
+Airseeker can be configured via a combination of [environment variables](#environment-variables) and
+[configuration files](#configuration-files).
+
+### Environment variables
+
+For example:
+
+```sh
+# Defines a logger suitable for production.
+LOGGER_ENABLED=true
+LOG_COLORIZE=false
+LOG_FORMAT=json
+LOG_LEVEL=info
+```
+
+or
+
+```sh
+# Defines a logger suitable for local development or testing.
+LOGGER_ENABLED=true
+LOG_COLORIZE=false
+LOG_FORMAT=json
+LOG_LEVEL=info
+```
+
+#### `LOGGER_ENABLED`
+
+Enables or disables logging. Options:
+
+- `true` - Enables logging.
+- `false` - Disables logging.
+
+#### `LOG_FORMAT`
+
+The format of the log output. Options:
+
+- `json` - Specifies JSON log format. This is suitable when running in production and streaming logs to other services.
+- `pretty` - Logs are formatted in a human-friendly "pretty" way. Ideal, when running the service locally and in
+  development.
+
+#### `LOG_COLORIZE`
+
+Enables or disables colors in the log output. Options:
+
+- `true` - Enables colors in the log output. The output has special color setting characters that are parseable by CLI.
+  Recommended when running locally and in development.
+- `false` - Disables colors in the log output. Recommended for production.
+
+#### `LOG_LEVEL`
+
+Defines the minimum level of logs. Logs with smaller level (severity) will be silenced. Options:
+
+- `debug` - Enables all logs.
+- `info` - Enables logs with level `info`, `warn` and `error`.
+- `warn` - Enables logs with level `warn` and `error`.
+- `error` - Enables logs with level `error`.
+
+### Configuration files
+
 Airseeker needs two configuration files, `airseeker.json` and `secrets.env`. All expressions of a form `${SECRET_NAME}`
 are referring to values from secrets and are interpolated inside the `airseeker.json` at runtime. You are advised to put
 sensitive information inside secrets.
 
-### `sponsorWalletMnemonic`
+#### `sponsorWalletMnemonic`
 
 The mnemonic of the wallet used to derive sponsor wallets. Sponsor wallets are derived for each dAPI separately. It is
 recommended to interpolate this value from secrets. For example:
@@ -27,7 +86,7 @@ recommended to interpolate this value from secrets. For example:
 "sponsorWalletMnemonic": "${SPONSOR_WALLET_MNEMONIC}",
 ```
 
-### `chains`
+#### `chains`
 
 A record of chain configurations. The record key is the chain ID. For example:
 
@@ -44,61 +103,61 @@ A record of chain configurations. The record key is the chain ID. For example:
 }
 ```
 
-#### `contracts` _(optional)_
+##### `contracts` _(optional)_
 
 A record of contract addresses used by Airseeker. If not specified, the addresses are loaded from
 [Airnode protocol v1](https://github.com/api3dao/airnode-protocol-v1).
 
-##### Api3ServerV1 _(optional)_
+###### Api3ServerV1 _(optional)_
 
 The address of the Api3ServerV1 contract. If not specified, the address is loaded from the Airnode protocol v1
 repository.
 
-#### `providers`
+##### `providers`
 
 A record of providers. The record key is the provider name. Provider name is only used for internal purposes and to
 uniquely identify the provider for the given chain.
 
-##### `providers[<NAME>]`
+###### `providers[<NAME>]`
 
 A provider configuration.
 
-###### `url`
+`url`
 
 The URL of the provider.
 
-#### `__Temporary__DapiDataRegistry`
+##### `__Temporary__DapiDataRegistry`
 
 The data needed to make the requests to signed API. This data will in the future be stored on-chain in a
 `DapiDataRegistry` contract. For the time being, they are statically defined in the configuration file.
 
-##### `airnodeToSignedApiUrl`
+###### `airnodeToSignedApiUrl`
 
 A mapping from Airnode address to signed API URL. When data from particular beacon is needed a request is made to the
 signed API corresponding to the beacon address.
 
-##### `dataFeedIdToBeacons`
+###### `dataFeedIdToBeacons`
 
 A mapping from data feed ID to a list of beacon data.
 
-##### `dataFeedIdToBeacons<DATA_FEED_ID>`
+###### `dataFeedIdToBeacons<DATA_FEED_ID>`
 
 A single element array for a beacon data. If the data feed is a beacon set, the array contains the data for all the
 beacons in the beacon set (in correct order).
 
-###### `dataFeedIdToBeacons<DATA_FEED_ID>[n]`
+`dataFeedIdToBeacons<DATA_FEED_ID>[n]`
 
 A beacon data.
 
-`airnode`
+`dataFeedIdToBeacons<DATA_FEED_ID>[n].airnode`
 
 The Airnode address of the beacon.
 
-`templateId`
+`dataFeedIdToBeacons<DATA_FEED_ID>[n].templateId`
 
 The template ID of the beacon.
 
-### `deviationThresholdCoefficient`
+#### `deviationThresholdCoefficient`
 
 The global coefficient applied to all deviation checks. Used to differentiate alternate deployments. For example: