message: make r2d2 optional
diff: @@ -4,35 +4,34 @@ edition = "2018"
  name = "connectorx"
  version = "0.2.0-alpha.3"
  -# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
  -
  [dependencies]
  anyhow = "1"
  +fehler = "1"
  +itertools = "0.10"
  +log = "0.4"
  +rayon = "1"
  +sqlparser = "0.9"
  +thiserror = "1"
  +
  arrow = {version = "4", optional = true}
  chrono = {version = "0.4", optional = true}
  csv = {version = "1", optional = true}
  derive_more = {version = "0.99", optional = true}
  fallible-streaming-iterator = {version = "0.1", optional = true}
  -fehler = "1"
  hex = {version = "0.4", optional = true}
  -itertools = "0.10"
  -log = "0.4"
  ndarray = {version = "0.15", optional = true}
  num-traits = {version = "0.2", optional = true}
  owning_ref = {version = "0.4", optional = true}
  polars = {version = "0.14", optional = true}
  postgres = {version = "0.19", features = ["with-chrono-0_4", "with-uuid-0_8", "with-serde_json-1"], optional = true}
  -r2d2 = "0.8"
  +r2d2 = {version = "0.8", optional = true}
  r2d2_mysql = {version = "18.0", optional = true}
  r2d2_postgres = {version = "0.18", optional = true}
  r2d2_sqlite = {version = "0.18", optional = true}
  -rayon = "1"
  regex = {version = "1", optional = true}
  rusqlite = {version = "0.25", features = ["column_decltype", "chrono", "bundled"], optional = true}
  rust_decimal = {version = "1", features = ["db-postgres"], optional = true}
  serde_json = {version = "1", optional = true}
  -sqlparser = "0.9"
  -thiserror = "1"
  uuid = {version = "0.8", optional = true}
  [lib]
  @@ -56,6 +55,6 @@ dst_polars = ["polars", "dst_arrow"]
  fptr = []
  src_csv = ["csv", "regex", "chrono"]
  src_dummy = ["num-traits", "chrono"]
  -src_mysql = ["r2d2_mysql", "rust_decimal", "num-traits", "chrono"]
  -src_postgres = ["postgres", "r2d2_postgres", "csv", "hex", "serde_json", "uuid", "rust_decimal", "num-traits", "chrono"]
  -src_sqlite = ["rusqlite", "r2d2_sqlite", "fallible-streaming-iterator", "derive_more", "owning_ref", "chrono"]
  +src_mysql = ["r2d2_mysql", "rust_decimal", "num-traits", "chrono", "r2d2"]
  +src_postgres = ["postgres", "r2d2_postgres", "csv", "hex", "serde_json", "uuid", "rust_decimal", "num-traits", "chrono", "r2d2"]
  +src_sqlite = ["rusqlite", "r2d2_sqlite", "fallible-streaming-iterator", "derive_more", "owning_ref", "chrono", "r2d2"]
  